I'm not a Harry Potter fan at all. I haven't even seen all the movies, and don't care much about any of it. But LEGO Harry Potter was my first LEGO game and I enjoyed ever second of playing it (probably had a lot to do with my co-op partner, but the game was really enjoyable). They make for a great two player experience, they are casual enough that someone who doesn't play video games can get into them, and fun enough that someone who plays a lot of games can enjoy them.

Plenty of parents play these games with their kids. References to films kids wouldn't/shouldn't get seems perfectly reasonable, these games may have originally been made as fun and easy kids games, but since then it has been well established adults play and love them too. Several years ago, before LEGO Star Wars and the following the series of themed LEGO games, I couldn't imagine too many adults having much interest in playing a game called LEGO: City Undercover, but I'm sure they anticipated it would ride on the reputation of the other LEGO games as fun for all ages.