I've heard a lot of people compare it to Wreck-It-Ralph, but I don't believe that's an accurate comparison. Both are animated, fun for the whole family, and have a feeling of nostalgia, but The Lego Movie has a whole different feel to me overall. I can assure you that it didn't come across like a commercial for Lego's, though it might naturally cause some feelings of your inner child architect to develop. It's super funny, the music is fantastic, and the characters are all likable and well-developed.
Spoilers under the cut.