I'm surprised to see so much love for Majora's Mask in here. I mean, I knew people liked it, but I always thought Ocarina of Time was the better game. I couldn't get over the fact you had to remain as kid Link basically the entire game. The whole plot was an interesting twist in MM though, I'll give them that.
As far as games I dominated, I was a beast at Goldeneye on N64. Aside from taking the time to unlock all the cheats, I usually destroyed my friends just enough and let them win occasionally so they would still want to play

Same thing with Mario Kart, up until the Wii versions, just never got into them and theres only a few people around to play since I was in college last time Mario Kart was popular lol. Speaking of college and Contra, I did witness a guy beat Contra on just the 3 lives and no continues. He also had no life...like, he lived in his dorm room.
Aside from those, I was pretty good at all the competitive Super Mario games and Punch Out (I've got a Play Choice 10 arcade in my garage these days with those games)
Here was a game I was really good at that hasn't been listed: Base Wars. Best Baseball game that has ever been released. Where else can you command robots on the field, and then fight to the death if they try to tag you out?