um, probably Lego Star Wars 2. I thoroughly enjoyed that game. It has the edge on Lego Indy on a couple of points, like how you can deflect enemy lasers with your lightsabre, and some levels, like Hoth and the Death Star, where both players can have their own vehicles, even though the fixed camera for both players makes the Lego Lucasarts collaborative projects perfect for losing friends.
What i miss is the ability for your mates to be able to pop into your vehicle and ride shotgun with a shotgun or something, because as has already been said, the fixed camera makes it an absolute nightmare, even if you do manage to find vehicles for both players.