Megaman 2. My three older brothers watched and cheered for me while a was battling to kill Dr. Willy. Dammit I felt like Jesus at an age of 10.

Rockn Roll Racing on SNES,
i where able to shoot them even they where not on screen! Hell yeah great time it was.

I think it was Pokemon Gold.

Well, as I said I was very young :P

Warcraft 2 or Duke Nukem 3D. In warcraft 2 I had to have 3+ friends against me. And in Duke Nukem 3D I wasn't allowed to use RPG. :)

I always thought the hardest was beating Facility on 00 in 2 minutes.  I must've played that one level for hours, and when I first did it, I took a photo of the screen to prove it to my friends.  I was gonna mail it into Nintendo Power but I missed the deadline.  Then everybody in my high school paid me a couple bucks to get Invincibility on their games for them.  At my high school I was the Goldeneye king.

Goldeneye was another game I completely dominated.  A few of my friends would refuse to play with me even with handicap levels maxed out.  Most would play with me though.  I'd put them at +4 health and myself at -4 health, and I'd be Jaws, and I'd still dice 'em up with an RCP-90.  Then I got so nuts I memorized all the respawn locations and could win one on one matches 10-0.  Then everybody gave up on playing with me.  Love that game.

Mortal Kombat and Street Fighter 2 (Arcade)

SP: Splashdown: Rides Gone Wild. I know it sounds kind of lame, but I beat the whole thing; unlocked everything, and did it all without cheat codes. I'm pretty amazing at that game.

MP: Ace Combat 4. I played that game a ton, and no one would ever do multiplayer because I just annihilated them. XD

super mario bros, i could beat the game without dying, i dont use the wrap pipes so my friends used to wait a long time.

first multiplayer game i dominated was World Cup Italia 90 on the megadrive/genesis, i was undefeated for a year in that game, no one dared to play against me, until my little sister beat me, i never played that game again, because i had lost my honor:P

Super Smash Bros. Melee. I kinda trained myself in that game for a year or so, and even though I couldn't do wavedashing or some other glitch tricks, I dominated in all other aspects. There was one friend of mine who could challenge me and sometimes win (though our record is still heavily in my favor), and those matches were plain epicness.