I'm not a gamer, but I still think this is awesome! There's a group working on a modification for Grand Theft Auto: Vice City that will turn it into "Back to the Future: Hill Valley." It'll be based on the trilogy and let you re-enact moments from the movies. Plus, you look like Mc Fly and get the Delorean.
Some of the Features that will be in Back to the Future: Hill Valley are:
5 different eras of Hill Valley: 1885, 1955, 1985, Alternative 1985, and 2015.
New Vehicles to correspond to the different times
New Peds to correspond to the different times
Spontaneous and Instant Time Travel
New effects and sounds to accompany the time travel sequences
Flying Hover mode for the Cars and Trains of the future.