I always thought of cheat codes as being there to mess around and have fun, but not to beat the game with. For example, I'd turn on invincibility in Warcraft and Starcraft just to explore the levels and find little Easter Eggs, but I wouldn't say I "beat the game" if I had it on the whole time. If it's aesthetically changes like big head mode or different costumes though, go nuts. TBQH, I find it more cheating to, say, spawn a tank in GTA than to use a cheating device to get the nature you want in Pokemon, but that's because I hate mindless grinding.
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