As a Resident Evil veteran, understand that the word disappointment is not strong enough to describe this movie.
First, the chronological order is screwed up. The STARS team was the ones that investigated the Spencer mansion. By the time Leon and Claire got to Raccoon City, the city was already infested by the T-virus. The events of Leon and Claire happen quite sometime after the Spencer Estate incident. Next, the STARS team showed all the members... except Rebecca Chambers and Barry Burton, who weren't important to the story but was still valuable members of the team. It was cool to see the main hall of the Spencer estate looked identical to the video game, so props for set design. The G-virus was also a closely guarded secret, only known by Birkin, Wesker, and Wesker's Umbrella team (Hunk and the others). Vickers doesn't die in the chopper, he dies outside of the police department (kinda goes with the problem of the chronological order). William Birkin has never met Chris Redfield. Jill and Leon have never met in any capacity. Jill was the one who played the piano, and that was after she was separated from the rest of the team (not that big a deal for the story, just a statement of fact). Chief Irons (if that is who the character in the movie is) never survived the police department (or the orphanage if you like the remake better). Lisa Trevor (a boss in RE 0) never left the Spencer Estate grounds and was not a helpful person, as she tried to kill Rebecca. The keys given to Claire in the movie are actually keys to the police station. The T-virus zombies could only be killed by headshots, not body shots. They did include the Ashford twins film, which was nice. The Ashfords, however, were not orphans. William and Anette (his wife) worked together to develop the G-virus, which never made it into the film (nor did the hive). Ada killed Anette, not Wesker. The Tyrant "killed" Wesker, not Jill. Chris didn't meet Sherry until the 6th video game, almost 20 years later. Jill has never met Sherry. Claire and Leon escaped Raccoon City with Sherry, not Jill and Chris. The city was leveled by a thermobaric missile, not whatever it was in the movie. Ada Wong played a much bigger role in Racoon City.
Next, we have characters. Albert Wesker, a member of STARS AND Umbrella, was involved in the Spencer Estate incident. In the movie, he's more relaxed and has no idea what's happening. Leon is far more serious in the games and responds to the RC incident as a true professional would. His character is poorly portrayed in the movie. Chris and Claire (who was only in Raccoon City to find her brother, who had disappeared) are closer than the movie portrays, being separated by age and the fact that Chris went into the air force, not because Claire was selfish and left. Ada Wong worked for Wesker, not the other way around.
Given all these game/movie comparisons, I do believe that as a Resident Evil title, this movie left much to be desired, as it essentially rewrote everything. As a standalone movie, this was not a bad watch. The people who don't know much about Resident Evil would definitely enjoy this movie.