While not the most varied game in terms of story or gameplay, the co-op more than makes up for it
The game art style which has been debated a lot, fits the game well. Sound effects are done well both voice acting and the weapon sounds. Gameplay is rather boring and repetitive, and the game suffers from a lack of bad guy variety. This means it can get kinda boring if you play solo. However, if you team up with a buddy via split screen or over the Internet, the game gets lots more fun, with harder enemies, and someone to pass the time mowing through the respawning hordes of enemies with.
As a single player affair the game is simply slightly above average, but it is in this co-op mode where it shines. Too bad none of my friends play the game, so I am missing out on the best part.