Hey you, yeah you reading this. If you don't have Borderlands 2 for whatever platform you own then go and buy it. I don't care if you've gotta go to Walmart or Gamestop or Steam or where ever, go and buy this game right now.
Here are a list of reasons if you actually need them;
orderlands lacked in story. It wasn't terrible, but it felt like it took a bit of a back seat compared to some of Gearbox's other games. Borderlands 2 on the other hand has one of the most engaging stories I've ever had the pleasure of playing.
I'm not completely done with the game, only a few chapters left to go, and I can honestly say that I've never been more invested in the story in any other game. There's been one point that I was almost in tears because of an event, and another time that I actually wished Handsome Jack, the game's antagonist, was right in front of me so I could actually tear him limb from limb.
Something else Gearbox does amazingly well in this one is write a villain you absolutely hate. Every time you set back his plans in some way it's satisfying, knowing you're screwing him over even a little; and every time he comes out on top you just want to scream because he's such an asshole.
The combat is incredibly fun, the guns and enemies and powers are all absolutely ridiculous. Take my current rocket launcher for instance, it does just over 10k per shot, has explosive elemental damage and when I reload the launcher itself turns into a rocket and a new one materializes in my character's hands. I have a sniper rifle that sasses off to me when I reload or get a critical kil, a burst fire assault rifle that covers enemies in acid...the amount of weapons and grenades is just overwhelming. Enemies are far more varied than before and actually require you to think about what weapons you'll be bringing into an area.
The soundtrack is, as usual, utterly perfect. It doesn't overwhelm the rest of the game but still helps to set the mood, especially during fights. (The small sting when a Goliath changes fits perfectly.)
The graphics are improved over the first game, but not by a lot. I play on the Xbox 360 which looks fine, but I've seen videos of PC gameplay and wow that is a massive improvement. I've had a few pop-in issues when I load a new area and I had a small area that the particle effects of a laser never went away, but other than that no major issues.
Overall the game is utterly fantastic and you should just buy it. Go. Stop reading this and give your money to Gearbox, it'll be worth it.