I personally really enjoyed the game, I liked how it filled in the blanks of the "behind the scenes", stuff you didn't get to see or know about during the actual playing of RE2 etc.
I liked the concept of it, and the team based co-op is something I always enjoy and like to see in games, only thing better than a good campaign is a good campaign with a co-operative option!
I do however have my gripes with the game, seriously its buggy as hell. I grit my teeth everytime I get onto an Elevator, I've had elevators mid-way to the destination suddenly just fall back down and sometimes go through the floor..... yeah, I've noticed most of the time these problems only occur with people in my game who are on a bad connection or are from a part of the world that is rediculously far away the connection is too choppy.
This aside though I think the game deserved to do a bit better, however I do feel capcom churned this one out a bit half asssed with all the problems it has. I think alot of other people, and reviewers for magazines have sensed that too and it is why it got the bad reviews it did. I personally think this game is a gem, a hidden one at that which most people who enjoyed the other in the series will overlook.