Both Lego Star Wars games are really fun. A little on the simple side, although some of the achievements in Lego Star Wars II are only going to be obtained from the hardxcore gamer. I really enjoyed it, and it's got some great replay value. Anyone can play and jump into it.
If you're looking to get it, wait until the end of this year. They're putting both games into one and adding some extra features not seen in either game. That'd be the most solid deal, I would say.