I forgot so many, but here's an initial list:
(nes)
Karnov
Hoops
Bad Dudes
Double Dragon I&II
Contra
Lifeforce
Jackal
Strider
Final Fantasy
Three Stooges
Legend of Zelda
Chip n Dale
Bionic Commando
Silkwurm
Street Fighter 2010
Mega Man I&II
Eight Eyes
Castlevania: Simon's Quest (the easiest one)
River City Ransom
Metal Gear
Snake's Revenge
Mike Tyson's Punch-out
Dragon Warrior
Kung Fu
Nightmare on Elm Street
ProWrestling (cheated w/NesAdvantage)
Intellivision
Astrosmash and Burgertime (I guess you could say I beat since I looped through the levels twice)
Bump n Jump (looped the levels once)
Advanced Dungeons and Dragons
Advanced Dungeons and Dragons: Treasure of Tarmin
Genesis
(I know I've beaten more, but I can't remember, plus I think I mostly played sports games)
Buck Rogers
Beavis and Butthead
Evander Holyfield (real deal boxing or whatever the fuck it was called... I whooped his ass without the cheat)
Snes
never had it or played it much, but I did beat:
Super Tennis... even beat Don J's ass, and much
to anybody who knows what I'm talking about.
x-box
Max Payne
Splinter Cell
Morrowind
Simpsons Road Rage
Star Wars KOTOR
DOA III
(arcade, computer, etc.)
Virtua Fighter II
Robocop II
Soldier of Fortune
TMNT
Dark Forces
Gabriel Knight
blah.