Also, health regeneration and limited weapons work so well in Borderlands 2. The RPG-ness make those fit in perfectly. Ideal place for it.
I hate hate hate 2 weapons, though. 4 is much better. I guess I'd actually prefer if Borderlands let us have 1 of each type queued up, which starts defeating the purpose of limited weapons. It's something that can work, but is clearly a console concession. It doesn't bother me in modern war games, either, where there's no reason to have more than 1 main weapon and 1 backup weapon, because you're creating a class.
In Halo it just felt wrong. Having to choose between a sniper rifle or a rocket launcher meant you rarely pick up the rocket launcher.