Borderlands 2 owns. It's everything the original Borderlands should have been. Not that Borderlands wasn't good - it was actually very, very good - but the game lacked the variety (loot, enemies, locales, level design, mission design) to stay engaging. I'm like 5 hours into Borderlands 2 and I've seen more weapon and enemy variety than probably the majority of the original game, and that's without mentioning the fantastic area design. The real treat are both the writing and loot - which are a tremendous step up - which makes the game feel more than the simplistic and absolutely uninspired go to point a, go to point b schlock that made up the original. Borderlands 2 makes uses of its humor in more interesting degrees.
Not that Borderlands needs extravagant writing, but it helps to get absorbed into a game that has all the details placed well rather than get the feeling it was written in the span of a week. But more than that, the loot is amazing and keeps getting even better. The elemental system keeps guns constantly involving and interesting to the point where you grow attached, rather than shelf it for the next more powerful weapon like in the original. I dare say Borderlands 2 gets loot games better than Diablo 3 based on my time so far.
Fantastic package all around. When I first booted it up, I was thinking,"well, this is Borderlands alright..." but the more you play sink your teeth into it, the better it gets.
Between Jet Set Radio HD, Dark Souls, and Borderlands 2, my pc is getting some nice use for gaming this fall.