I've never actually played the Silent Hill game, but the movie was one of the creepiest things I've ever seen. I don't know if the game is as creepy, but the movie certainly is not for the squeamish.
Another bad one: Parasite Eve. The movie had almost NOTHING to do with the game at all!
Yeah, Wing Commander was a game series first. Made by Origin Systems, makers of Ultima. It's a space combat game similar to Tie Fighter vs X Wing. (but made way earlier) I only played the first two. I didn't know there was an animated series, I will have to look for it.
The Final Fantasy anime was very strange, and didn't seem to have much of a connection to the games. I rented the first disc from a comic shop. My reaction was "WTF is this?!" Didn't bother to watch any more.
I would like to watch Parasite Eve, but it's currently in Netflix Limbo.
I enjoyed the Silent Hill movie. I don't know much about the game series to compare tho.
I really want to see what they do with the Metal Gear movie, I think I could be really good. Hell, MGS2 is mostly a movie anyway. However, I'm afraid that anyone besides David Hayter for Snake's voice just won't do! :P
Just wanted to mention here that I just watched the second Silent Hill Movie (Silent Hill: Revelations) and, while not quite as good as the first, was still very creepy. They have me wanting to try the game, now.
I've noticed that not much has been said about the Resident Evil movies....