And I'm gonna be in the minority here but "Piper" gets a second place vote from me. For some reason I always loved that album, perhaps because I've always been so intrigued by Syd Barrett's story, so his music interests the shit out of me.
But they're all excellent. I love Pink Floyd, but as I just said to a friend the other day, I need to be in a very specific mood to listen to them.
I prefer the earlier stuff anyway. I actually think More and Obscured by Clouds are better than Meddle, even.
I like the mid/later 70's stuff (especially Dark Side of the Moon), but I have always preferred the pre-Dark Side albums. Maybe just on the strength of their unfamiliarity. **shrug**