I loved the LEGO Star Wars games to death. THEY WERE AMAZING! (Still haven't played the Clone Wars game though)
LEGO Batman (the original) was pretty darn fun. Punching henchmen to plastic bits gives a certain twisted satisfaction. Also, the soundtrack and atmosphere in that game was great.
LEGO Indiana Jones was also very enjoyable. I only played a bit of Indy 2 (wasn't a big fan of the open-world hub).
Speaking of confusing open-world hubs, LEGO Harry Potter's Hogwarts was the worst. The levels were fun, but I got lost way too many times in that castle.
Me and a buddy were goofing off in the Marvel Superheroes game a little while ago. Spider-man's web-slinging was a ton of fun.