Great campaign, decent competitive mp, but amazing co-op sets this game apart.
The campaign is lots of fun with a great variety of weapons and hordes of enemies to slaughter. It improves on the first with its sense of scale and actual bosses to defeat (the first had no bosses to speak of). The music kept me on edge and excited throughout the entire single player experience. Graphics looked nice, not the best on the PS3 but definitely not the worst. The one thing that the campaign lacked that the first one had was co-op through the campaign.
The competitive mp is fun in short bursts. The map design is nice. The competitive mp doesn't give a whole lot of incentive to keep playing and leveling up though.
The star of this show is the online co-op. You go through little episodes with up to 7 other players completing tasks and taking down tons of enemies including bosses. There are three classes to choose from and separately level up to get new gear and weapons. It is very addicting and satisfying to take down huge bosses with other players around the world. There is still a lot of people playing as well. This is where I have spent most of my time with this game.
Overall this game improves on the first in every area. I wish there was co-op for the campaign but that is one of my only complaints. Great sequel and a great game.