This is the most fun I've had with a controller in years. Lego Star Wars II allows you to play through Episodes IV-VI, with each movie divided into six levels. The real charm is not in simply playing through the story; it's in replaying it.
The replayability comes from the challenges you face in each level, many of which can only be met by repeating the levels with different characters. For instance, there are several areas you can't access without a Bounty Hunter head, a Storm Trooper helmet, or access to the Dark Side of the Force. It's rare for Luke, Leia, Han or Chewie to have such things, so the game's designers added a feature: the ability to hack together a new character with the parts and powers of other characters. Combine different body parts as you did as a kid with actual Legos, add in a few special powers, and voilà: Soon you can start replaying those early levels and collect all the bonus items you need to complete the game.
With Lego Star Wars II, you can become the popular uncle or aunt who kicks ass at the kids' favorite game. Or you can just become that weird guy who's always going on about Lego Star Wars. Trust me, the teasing doesn't bother you after a while.
