It depends on how you look at it. For example, if your stuck on something then you can use a cheat to beat it effortlessly so in that way it helps you (good), but now the game isn't really fun and is less challenging cuz you wont really try because you have the cheats to take advantage of-that makes it less enjoyable so I think that reason makes it bad too. Anyways I think like many other stuff in the world, Game cheats have their benefits and disadvantages. :]
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
