Builds on, while improving its predecessor.
Cons: somewhat limited enemy line-up gets repetitive quickly
Borderlands 2 doesn't stray too far from the original game, but rather opts for some much-needed tweaks to the previous formula. However, these seemingly minor modifications go a long way in make B2 significantly better than its predecessor.
I especially enjoyed the move to flesh-out the NPCs that populate the game, while giving (limited) background into the four character classes. While the requisite (and seemingly infinite) selection of firearms, shields, mods, and grenades return, the variety of each weapon seems more thoughtful, with variations running the gamut from different types of elemental damage to firing arcs.
Last, I've only had the time to play the Captain Scarlett DLC, but I've been impressed with Gearbox's ability to create DLC that feels like a mini-game, but still ties into the larger universe.