To me, it's the best series to adopt the Diablo loot/randomization system, (among other features that are derived from Diablo) and easily the best first person Diablo-esque game. The AI and enemy repetition are the only major faults I can think of, but it's not like my beloved Diablo is any better in that respect. I'd recommend Borderlands to anyone who enjoys both RPG and FPS games; this game truly is a pure mashup of said genres. There are the Bioshock games, which have RPG elements, but lean more towards being shooters, and you have Fallout 3 and NV, which lean more toward the RPG side, and Borderlands feels right in the middle to me.