This all depends on the game, GTA is nice in single player to do a weapon cheat to get all the guns, or the tank cheat when you want to get all 5 stars.
Sometimes I find cheat supplemental to the experience.
For example: San Andreas. Since I pretty much can't get past flight school (I guess the controls simply don't work for me... I can never learn some of the advanced stuff. As soon as I "turn" a plane, I'm screwed)... I rambled. Since I can never beat the actual game... I turn on "NPC's have guns", "Crazy Driving" and "Civilian Riot"... And watch the entire world go bat**** insane. I even wrote a short story regarding my experiences. It was very interesting.
I think gta and oblivion are the only games I cheated in. But just because gta is hard since I die all the time and oblivion has a worthless money system