The question is mute. Imho, all of them together are better than anyone else in each their own ways. But if I had to choose, then The Wall.
Every album has its merits except Momentary Lapse of Reason which is pretty dreadful. I think choosing one album is difficult because the band changed so much over the years...there's the psychedelic phase which ended after a few albums (although traces of it can still be heard all the way through to Dark Side), the avant garde phase, the prog phase, the pomp phase (The Wall, The Final Cut) and the crappy Gilmour phase. My favourite? It's a toss between Piper, WYWH, Animals, Dark Side and The Final Cut. Saucerful, More, Meddle and Obscured by Clouds are all great albums too though.
That's like asking me to choose my favorite child!!! C'mon! It makes me queazy just to think about it. I couldn't do without any Floyd album.
I love piper at the gates of dawn . It's my favorite ablbum of all time... and i absoaloutly love Syd!
Ummagumma, A saucerful of secrets, Dark side of the moon. Animals and the wall are basically roger waters solo albums still great but animals didnt have enough imput from the other guys thats why dave and rick made solo albums in 1978 because roger wouldnt take any of their material for animals.