It depends on what cheats you use.
If you use "Infinite Health", or "Unlock Everything" codes, it's not fun at all.
But if you use codes like "Play on Test Level", or "Moonjump", it's very fun, as there's more to discover in a game, than you normally can.
Inorite? It's also pretty fun to use the infinite Flying Mario code in SMG to explore more of the Galaxy and the models that aren't bein' used for certain missions (like Kaliente's planet in Dino Piranha's mission.
I think it really depends on when you use them, what game you're playing, and what the actual cheat is. "Unlock everything" codes are fine, but should ONLY be used after you beat the main story. If you start from the begining with level-40 weapons or attacks, it's just not fun. I personally like cheats that let you screw around with the game without making progress in any way, like those cheats that let you change Mario's colour palette or access planets in SMG that can only be accessed through cheating. But if you're relying on cheats to let you finish the game faster or easier, it saps all the fun away.
As most of the others said, cheating for fun is what it's all about. Cheating to win defeats the entire purpose of the game. The MKWii cheaters are hilarious as long as they drop back to last at the very end. Moonjump and walk through walls cheats are fun until you glitch up your game and have to reset :l
I abstain from voting because of the subjective nature of the terms "good" and "bad." As far as cheating goes, I haven't done it in years (excluding stealing the bow from the shop in Link's Awakening ), but I think that unless it's done after the first playthrough of a game, cheating detracts from one's overall enjoyment of said game.