I used to love Paint it Black when I was younger but I prefer Gimme Shelter now.
It's an excellent opening track in 'The Departed' film.
There's also a good back story behind the writing and the recording of the song.

As far as the original topic goes, I never liked Pink Floyd when I was a youngster preferring Black Sabbath, Deep Purple, Led Zep and the much heavier stuff at the time but have come to appreciate them now.