Kevin Spacey plays an alien, Prot, from the planet K-Pax. Of course, he gets moved into a psych ward immediately where he's treated by a psychologist played by Jeff Bridges. All the actors were on cue, no false notes. The psych keeps being confounded by Prot, but also tries to find out who he really is. The movie has drama, comedy, romance, SF, just about everything, and all in the right places and amounts.
Be sure to watch through the credits for the ending. It then presents you with an alternate ending and I liked the first one. There were some other odd things for me -- I was thinking I'd watch In Plain Sight last night, but there was a Burn Notice marathon instead. However, the protagonist from IPS is Bridges wife in this, and a good part. Also, Brian Howes plays an astrophysicist in this, and I've seen him in lots of episodes of TV shows.
This is a movie that I think everybody would enjoy.