Stone Cold Steve Austin ... Hulk Hogan ... Shawn Michaels ... Bret Hart ... Hell, even John Cena. There is an argument to be made in regards to each and every one of these men being considered the greatest WWE Superstar of all time. Each has contributed a great deal to the company and have left behind legacies that will never be duplicated. One of a kind in their own regard.

However, we are here today to make the case and hold true to the belief that the greatest WWE Superstar of all time is and perhaps forever will be, The Undertaker. For the past twenty-five-years "The Phenom" has been the one steady heartbeat, that one consistent thump echoing throughout the WWE Universe. When that gong hits, everybody knows that The Undertaker is about to enter the scene.

While only working a part-time schedule in recent years, The Undertaker still works more dates than the aforementioned legends. The Undertaker has literally spent half his life under the employment of Vince McMahon; a solider of the WWE Army through the best and the worst years. There is something to be said about a man with such integrity, a man more loyal than most in a money-driven industry.

On a personal note: I had concluded some years ago that the greatest WWE Superstar of all time was Stone Cold Steve Austin and this held true until recently. The twenty-five-year anniversary celebration of The Undertaker has changed that perspective and while Stone Cold will remain the favorite, the distinction of "greatest" definitely belongs to The Undertaker.

The reasons are vast and entirely justified as The Undertaker is not just another WWE legend but the WWE legend. The following is a tribute to "The Deadman." A list devoted to the "Demon of Death Valley."

These are the top 15 reasons The Undertaker is the greatest WWE Superstar of all time:

15 15. One of a Kind 

via bleacherreport.com
via bleacherreport.com

You hear it said often: "that guy is one of a kind." However, how often is such a statement the full-on truth? In the wrestling industry, many of these mammoth men are expendable.

Far too often, wrestlers are replaced and forgotten; left to rot in the obscurity of the professional wrestling vault. Can such a fate await The Undertaker? Never. The Undertaker is a true original. That one of a kind character we will never find again.

14 14. Made an Oddball Character Something Legendary 

via riverfronttimes.com
via riverfronttimes.com

Remaining with the concept of character, let's be honest: those who witnessed the early days of The Undertaker probably didn't think much of the man behind the darkness. At first glance, The Undertaker was simply another character bordering on ridiculous.

However, Mark Calaway (real name) made The Undertaker work. Calaway brought about a new sense of fear throughout the WWE; a believable sense of fear that has maintained the attention of fans for the past twenty-five-years.

It is safe to assume that no other man would have been able to take this living-dead gimmick and turn it into something legendary.

13 13. Mystique Behind the Man 

via twitter.com
via twitter.com

Who exactly is Mark Calaway? I have tried to answer that myself in the past but the mystery remains. The man behind the rolled back eyes is more of a blur than most WWE Superstars.

While many of the greats have lead lives of lunacy and chaotic condition, Mark Calaway has more-or-less flown under the public radar, which is a difficult task considering the chosen career of Calaway.

Mystique means a lot to people; it draws them in more and more. It's why people remain fascinated with Bob Dylan after all these years and it's why fans will remain drawn into the mystique of The Undertaker.

12 12. First Ever Matches 

via ringthedamnbell.wordpress.com
via ringthedamnbell.wordpress.com

Whenever a wrestling promotion introduces a new match type to its audience, there is always a chance that the bout will fall flat and prove to be a failure. This is why it is essential to choose the right participants.

The WWE has placed a lot of faith in The Undertaker over the years as "The Phenom" has competed in the first Hell in a Cell, Buried Alive, and Inferno matches; each of which would prove successful for the company.

On the flip side: The Undertaker has also competed in the first ever Punjabi Prison match but we will simply overlook that disaster.

11 11. The Judge 

via commons.wikimedia.org
via commons.wikimedia.org

There are a lot of interesting things going on backstage in WWE. One of these things is something known as "Wrestler's Court." What exactly does that mean? Simply put: the talent hold their own court-like proceedings to resolve any backstage issues.

However, how would the boys in the back go about choosing the proper judge? They would definitely need a man of integrity and a man with more balls than most: bring in The Undertaker; the chosen judge.

That fact that your peers are willing to place decisions in your hands displays a level of confidence not easily found.

10 10. Willingness to Work with the Next Generation 

via bleacherreport.com
via bleacherreport.com

A true testament to The Undertaker is his wiliness to work with the up-and-coming stars of WWE. Back during the brand extension, The Undertaker remained a member of the SmackDown roster when he could have easily gone to Raw if he wanted.

During this time The Undertaker would work with the next face of WWE, John Cena but would also do something for the career of a young Superstar that is truly admirable as The Undertaker would put over "The Next Big Thing" on more than one occasion.

While The Undertaker and Brock Lesnar feud has recently culminated, The Undertaker played a pivotal role in getting Lesnar over some years ago.

9 9. Willingness to Assume Spots 

via alternativenation.net
via alternativenation.net

During the Monday Night War, everything was up for grabs; including spots that were once owned by certain Superstars. In WWE, if you weren't finding a way to make something happen, then you would lose your spot.

While The Undertaker has played on the main event field many times, "The Deadman" has also assumed roles underneath to top of the card. Perhaps working with those considered "mid-card status" or working the tag team division.

Instead of wielding his political pull - which is done by many - The Undertaker would role with the punches and do whatever necessary to help the company.

8 8. The Streak 

via ultimatesportstalk.com
via ultimatesportstalk.com

For those old-time WWE fans, the 2,803 day WWE Championship reign of Bruno Sammartino will always be considered the greatest record in WWE history. However, those old-timers are not likely reading this, so let's focus on something else.

Foe the millennial WWE fan, there is perhaps no greater record than the famous WrestleMania undefeated streak set by The Undertaker. Until Brock Lesnar came along, "The Streak" stood at 21-0.

This is something WWE will likely never do again with any of its Superstars. Expect this record to remain unbroken.

7 7. Character Evolution 

via toovia.com
via toovia.com

It happens all the time in the wrestling industry: characters undergo a shift, a tweak, or a full-on makeover. The Undertaker character has come a long, long way from wearing purple gloves and a necktie.

The Undertaker has evolved more than anybody over the years as the character would fit into every era from its inception. This is by no means an easy task as even the slightest change can sometimes doom a character.

Think about the American Bad Ass gimmick? Who else could have pulled off such a drastic character shift?

6 6. In-Ring Ability 

via pwmania.com
via pwmania.com

In terms of in-ring ability, The Undertaker is a rarity. There are not too many men who stand and weigh close to seven-foot and three-hundred pounds who can do the things The Undertaker can do.

Most big men are slow and flimsy on their feet. The Undertaker on the other hand, holds his own no matter the size of his opponent. Size often dictates the length of a career as men of a bigger frame are usually prone to enduring more pain and shortened time.

However, The Undertaker has battled through almost every hurt a wrestler can endure and is still standing tall (literally and figuratively).

5 5. Defeated Legends 

via voicesofwrestling.com
via voicesofwrestling.com

You know the old Ric Flair line: "to be the man, you have to beat the man." Well, The Undertaker has beaten every "man" WWE has offered for the past quarter century from Shawn Michaels, to The Rock, to Triple H, to Stone Cold, to Ric Flair as well.

Legends are placed beside other legends, as wrestling is defined by those who leave the most impact on the business. The Undertaker has fought every big name in every circumstance and has always emerged better than before.

It is no coincidence that The Undertaker would even defeated Hulk Hogan after only one year in WWE. The future had already been dictated.

4 4. Longevity 

via dailyddt.com
via dailyddt.com

Doing anything for twenty-five-years can prove a tedious task. In wrestling, surpassing the twenty-year marker as an active competitor is tough but has been done by many. However, most are rendered beaten-down pieces of stale meat.

The Undertaker has his share of bruises and broken bones to show for his many years of service to the industry and just like many of his peers, has physically felt the wrath of being a professional wrestler.

What separates The Undertaker from the crowd is the fact that these past twenty-five-years have been specific to WWE.

3 3. Loyalty 

via twitter.com
via twitter.com

Keeping with a career specific to WWE: there is something to be said about a person who displays loyalty. Not the false social media "loyalty" to which this new generation has become accustomed to, but good old-fashioned loyalty.

The Undertaker was never going anywhere back in the '90s. WCW could have came calling every other day with a more lucrative contract each time but The Undertaker was going to remain put in WWE.

There has never been a more loyal soldier to Vince McMahon and his company than The Undertaker.

2 2. Lasting Legacy 

via cheap-heat.com
via cheap-heat.com

The Undertaker has cast an aura over the WWE Universe that will never fade. In fifty years, fans will continue to speak of "The Phenom" and all he had accomplished during his time in WWE.

The Undertaker was not just a flash-in-the-pan Superstar. The Undertaker made that pan so damn hot that it burnt and scared your hand upon touch; leaving an unforgettable reminder that The Undertaker was here.

There are plenty of WWE legacies that will last forever but none with quite as much prestige as that of The Undertaker.

1 1. Respect 

via prowrestlingstories.com
via prowrestlingstories.com

You may have heard the saying: "respect is earned." This is a true statement. You don't just hand out your respect with blindness. Respect means (or at least it should) a lot in any industry.

Show someone the proper respect and we are halfway home to a decent society. In that WWE locker room, no one has earned more respect than The Undertaker. The greatest of the greats have the utmost respect for The Undertaker.

Is this enough reason to classify The Undertaker as the "greatest WWE Superstar of all time?" You're damn right!