The main complaint I heard about it was that it was a little slow, not too much action. True, for the most part, but throwing in non-stop action would have turned it into something a-la Resident Evil. The point of the movie was he was trying to survive, and not fight, instead of fighting everything in his path. Really awesome.
Then, after a little more web browsing this morning, I thought of something that could be utterly amazing, or absolutley horrendous: I Am Legend the Video Game. That could have the potential to be amazing, if done right (which is wishful thinking, I know). Just think about how cool that would be!