The first movie wasn't bad on its own. Granted, from the perspective of a Resident Evil fan who subscribes to a great deal of the actual scientific and biological facts that the games are littered with, I found a lot of inconsistencies. (Lickers do not mutate by feeding on "fresh DNA". Eating people never contributed to any mutation overload with the T-virus)
There was also the outright ridiculous. (Alice wall-kicking a Cerberus and knocking it out cold in a grand display of an over-excessive need for action)
Thing that was okay with a lot of Resident Evil fans was that, even with the instabilities they displayed apart from the actual game mythos, the plot could very well have worked by itself in the canon of the Resident Evil games. It messed with very few actual established game characters and areas. If greater attention to detail had been given, it would have been fine to keep as a stand-alone movie in the Resident Evil universe. (kind of like if RE: Survivor had been made a movie)
But then the studios decided to give into fan desire for actual live-action depictions of canon RE characters and events, and made the mistake of thinking Paul Anderson and his writers were actually going to adhere in any way to the games story and that he wouldn't shove his wife into the spotlight as the Super Mary-Sue that outshines all others.