Oh my god, I think you may be my gamer doppelganger! Yeah, character creation, diversity, story and gameplay are what get me. Has to be an epic combination of those things. The Mass Effect and Dragon Age series are prime examples of that. I also like the Elder scrolls, Fallout, and Assassin's Creed for that too (Though obviously AC doesn't have the character creation, but I do like the customization in it.). I'm far from a completionist. I've started Skyrim a good 15 times by now, and I've only completed the main story twice. It's all in the journey!