Borderlands, probably.
It has its own style. There is really nothing like it out there. I like the characters, I like the universe, I like the humor, I like the weapon-hunting, and I like the elemental system (for the most part).
Of course, that's only assuming Fallout doesn't count, as I know some people get huffy about genre designations. If Fallout does count, then my list would probably look something like this:
Fallout
Borderlands
Far Cry
Deus Ex
Those aren't just some of my favorite FPS series, they're some of my favorite franchises in gaming. The FPS hate is silly.










