Definitely worth getting these two then. Mirror's Edge was a breath of fresh air and GTA4, although not as good as the very best GTA games, was still an awesome game in its own right.
GOW2 was very good although I didn't enjoy it as much as GOW perhaps because it was too similar.
As far as racing games go you can pick up PGR4 on the cheap and Forza 3 is release very soon. For skateboarding games I would look at the likes of Skate or Skate 2.
Edit: Although not really essential you could also have a look at some Live games like Shadow Complex, Braid and my personal favorite Worms 2: Armageddon