Austin vs. The Rock at WrestleMania 15
I think their match at 17 was even better, but it also had a much stronger undercard (TLC II, Taker/HHH, Angle/Benoit). WM15 was almost entirely about the main event, and it definitely delivered. Rock/Austin was the best match on the show, and it was the reason people ordered the show in the first place.
John Cena vs. CM Punk at MITB 2011
This match is maybe the best example of a huge buildup and payoff. Easily my favorite match in the last 10 years at least.
Hogan vs. Warrior at WrestleMania 6
The epitome of a WrestleMania main event that lived up to the hype. The two biggest babyfaes, the two champions, a classic match. Mania 6 was another show built entirely around one match, and the mach delivered in a big way.
John Cena vs. Brock Lesnar at Extreme Rules 2013
Brock's return to the WWE, and one of the best matches of all-time. The build emphasized Brock's realism and legitimacy and the match did as well. It seemed more like a real fight.
The First Ever Elimination Chamber at Survivor Series 2002
Couldn't even tell you what else was on the show. Shawn Michaels completes his comeback by winning the World Title. A great match and a great moment.
Triple H vs. Cactus Jack in a Street Fight at Royal Rumble 2000 and in a Hell in a Cell Match at No Way Out 2000
One of my favorite feuds. Again, these were the two most heavily promoted mathes on their respective shows and they were both home runs. They drew money, were crazy to watch, and they established Triple H as a top guy while giving Cactus jack one last run in the main event scene.