Have never played Borderlands.....quickly, describe it to me in a single sentence!
In a single sentence:
RPG with humor and lots and lots of freaking guns.
In detail:
It's a self-described Role-playing shooter. Story kind of takes a backseat to humor and old-school RPG-style looting everything that's not nailed down for the sake of getting your next shiny, possibly flame, acid, explosive, or electricity-shooting gun. Guns are generated using a procedural generation system that randomizes stats and things like sights, etc, on the guns so you will never get the exact same gun twice. Also, there's an enemy called Mutant Midget Psycho. Just throwing that out there.