People enjoy games in different ways, so using a Game shark and cheating is perfectly viable. It doesn't make you any less of a gamer, the same way there isn't any difference between someone who plays a game on insane difficulty compared to someone who plays on easy.
Some random things of note:
Sometimes the computer cheats, so cheating might even the odds a bit. (Puzzle Quest AI cheats horribly...)
Alone in the Dark 5 will apparently include a feature that allows people to skip the hard parts of the game if they want to. Link here. Developers give people tools to cheat a lot of times, so I don't think there is any reason to call someone who does so "not a gamer". They just enjoy the game a different way.