If you end up liking SR3 and want to continue on with the series, it might be a good idea to play the first two games before moving on to SR4, as there's a lot of references to the earlier games scattered throughout SR4. I've never been able to play SR1 since it was never released on PC, but I had a blast with SR2. While the engine's not as purty as SR3/4's (and it's supposedly one of the worst PC ports ever,) there's WAY more depth, detail, story and gameplay in it. SR3 feels really shallow by comparison. Definitely worth checking out.