I like playing games that give you a bonus once you beat it. Some games do this in the form of cheats, others let you replay the game with a funny character different costume... I really don't care what it is, I just want a reward for beating a game. The medal of honor games for gamecube that I've played have cheats in them, but I just recently beat MOH European Assault and I got nothing! Absolutely nothing! I was like, ok I beat it now, now what? There was no reason for me to go back and keep playing or anything.
I like to feel a sense of accomplishment when I beat a game, and being rewarded just makes me feel like I got an exclusive feature to a game.
Plus, it's fun. I like cheats where guns shoot photon beams and such. And I like it when they give you bonuses like the original game that came out on two or three systems ago. Like Metroid Prime did.