The biggest match all time at WrestleMania ?? Its Hogan-Andre and not even close. Andre was THE MOST POPULAR wrestler on the planet, he was bigger than Hogan, Dusty Rhodes, Bruno Sammartino, he was a beloved fan favorite Icon with a 20 year undefeated streak. When he turned heel and sided with Hogan's arch nemesis Bobby Heenan, a guy who's whole WWE career was built on trying to find someone, anyone who could beat Hogan, this was epic. It was bigger than Randy Savage crushing Steamboat's windpipe with the time keeper's bell, bigger than The Horsemen breaking Dusty's leg in the cage, this was huge. I'd say it's easily in the Top 5 biggest grounbreaking moments in the wrestling since 1980, right up there with the ascension of Stone Cold, Hogan's NWO Heel Turn, and Flair joining WWE and defending the World Title at WrestleMania.
Until WM 3, the event itself really was just WWE's version of Starrcade. In fact it's been documented in interviews over the years that the whole concept of WM really was just a take off on what Dusty Rhodes as booker had done making Starrcade so successful. WM 3 took the event, and WWE to another level of pop culture acceptance and financial success that no one could have imagined.
The card itself was OK, you had Roddy Piper's supposed Retirement Match, the highly anticipated Savage-Sateamboat clash, and 7 Time World Champion Harley Race making his WrestleMania debut. Still, that main event was transformative, if anyone was beating Hogan it had to be Andre, Hogan was at his height of popularity, Andre was a mega star. The hype was phenomonal. The fact this event drew a live crowd over 93,000 which was a North American Indoor Attendance Record at the time is a testament to the popularity of the show and the main event.
There have been a lot of great matches that had significant impact on the future of WWE and the industry as a whole or bouts that represented SuperStar dream matches we never thought we'd see but no single match had a greater impact on wrestling as a business and WrestleMania as an event that Hogan-Andre WM 3.
Far below that I would think the following matches deserve honorable mention in no particular order...
Flair/Savage - Two of the biggest stars of the 80's in a dream match no one though would happen, great storyline build, great match, one of the few WM's where Savage was allowed to not only shine but actually win. That alone makes it special, add to it Flair's long over due WM debut and this bout was special.
Austin/HBK: Austin's rise to superstar status was epic, and it was time for him once and for all to conquer McMahon, DX, and every other obstacle in his way to finally win the World Title outright. HBK has a nasty backstage rep for refusing to put over other stars and stories exist to this day that he wanted to back out of this match due to legit back injury but McMahon warned him he'd never work in WWE if he screwed up this main event, so he went out with a seroud injury and put forth a solid, entertaining, back and forth match that put over Austin cleanly as World Champion. Lets not forget that the post WM RAW was the first one in nearly two years that actually beat Nitro in head to head ratings, ending WCW's incredible 83 consecutive weeks winning streak in the ratings. This is where the tide turns in WWE's favor for the first time since 1995.
HBK/Hall Ladder Match: Did more to popularize the ladder match than anything before it or since. Also establshed HBK as a performer capable of wrestling any kind of match vs any kind of opponent. His ascension to the top of the ranks really kicks into gear here.
Hogan/Warrior: Definately an epic in it's time, the way Warrior's career unfolded doesnt take away from the significance of this bout, it was Hogan's first clean loss since first winning the title 6 years earlier, and showed the immemense popularity that Warrior had achieved. This might be Hogan's 2nd biggest WM match, just ahead of his title win over Randy Savage.
HBK/Hart Iron Man Match: WWE actually rewarded to smaller sized, skill based wrestlers not only with the main event, but with an Iron Man Match for The World Title! Not only one of the great World Title Matches of all time, this match marks the beginning of HBK's permanent rise to the top of the company. Hart remained a valuable presence but it was clear from this point on that HBK's charisma and mic skills had elevated him past The Hitman. It was a turning point match in both men's careers and would have profound impact on the start of The Attitude Era a few years later.
Austin/Rock 2: One of the most highly anticipated rematches of all time, easily the wildest and most entertaining of their three WM showdowns. This is also where the unthinkable happens, Austin sells out to his most bitter arch rival, Vince McMahon, leading to one of the great screw job finishes of all time and completely turning the main event dynamic of WWE upside down with Austin as the hated heel champion under McMahon's control. Not as big a surprise heel turn as Andre or NWO Hogan but pretty close.
HBK vs Retirement Matches: Simply put, two great shows featuring all time legends in matches that from the very first move felt like something special. HBK vs Flair was about a great as send off as anyone ever could have gotten, and was probably the best match anyone will ever see pitting an 40 year old vs a 59 year old, but the matchn had a quick pace, multiple momentum swings, and surprising athleticism given the age of the combatants. The ending will long be remembered as one the endearing moments, iconic moments ever at WM. HBK-Taker II had a similair feel, but the true test of why both bouts were unforgettable classics is that even though in each match you pretty much knew how it was going to end, the wrestlers involved made the matches so entertaining that they kept you glued to the screen regardless and really made you second guess yourself thinking, maybe the other guy really will win ?? The fact that two legenday careers came to a close and one incredible winning streak lived on makes these bouts among the most important in WM history.