Contrary to almost everyone here I have the first one for Xbox360 Then again I don't have Gold, at least, not yet.
I find adding rpg elements to games make it more interesting. Which makes this the only FPS series I'll pretty much ever own. Unless someone else comes out with something similar that isn't pretty much a clone. I think the names given to the guns and their abilities make it pretty fun to go through, that and I get to snipe people's heads off while leveling up.
Favorite Character: Mordecai
Favorite Weapon: Reaver's Edge, has one of the best scopes ever.