I felt very middle-of-the-road about this movie. Not because I lacked any real feelings on it, but rather I had different ways by which to judge it.
As a sequel, this movie succeeded hands down, since I found it much better than the first movie. The action, plot, characterization, and pacing was all better. The only part of the first movie I liked more was the ending cliff-hanger. However, this one was certainly unexpected, and is interesting.
In terms of how true this movie was to the games, though, I feel it was still, ultimately, a failure, though by a much lesser margin than it's predecessor. For one thing, it just didn't capture the feel of survival horror. The games succeeded in making you feel isolated and alone, and quite overmatched. This, however, felt more like an action film than anything else. This movie made you want to jump in excitement, whereas the games made you want to jump in fear.
Honestly, I don't want to fault the movies for that, but it seems unavoidable. Movies such as this play off of the popularity of the games, so some level of connection is expected. Therein lies the problem. Too much material from the games, and people complain it was nothing new. Not enough, and people say that it wasn't really about the game in the title. I don't think I've seen a movie yet that finds a workable middle ground.
On another note, I strongly recommend the novels Resident Evil: Genesis and Resident Evil: Apocalypse, which are the novelizations of the two movies. They're quite well done, and present a much more holistic view of the entire plotline between the two films than we saw on the screen.