Resident Evil is a 2002 science fiction horror film based on the same titled series of survival horror games developed by Capcom.
Borrowing elements from the video games Resident Evil and Resident Evil 2, the film follows an amnesiac heroine Alice, and a band of Umbrella Corporation commandos, as they attempt to escape a secret underground facility that at one time was filled with people, but is now overrun with zombies.
The movie differs from the video simply because of the medium and cannot be transferred literally. A movie cannot have the same storyline as the game and make it interesting for the player/viewer.
The movie itself has a pretty weak storyline with predictable twists, but is nonetheless very watchable. Without giving any spoilers, I can safely say that this is an action movie with zombies instead of a zombie film with action.
Mila Jovovich is great as the heroine and carries the whole movie.
If you liked the game, you should watch the movie as a bonus to the games, but also as a fun action zombie flick.