I like Animals because of the songs. I've always liked longer songs, not because I'm impressed by long songs, but because it allows time to explore different ideas within the same tune, maybe do some theme and variations, and of course give the instrumentalists a chance to stretch out. It's like the difference between writing a sentence about something and writing an essay about it.
A fully-formed three-minute pop song can be a masterpiece. Present the idea, wrap it up, move on. I'm just more impressed and more drawn to songs which fully explore the idea, present different sides, come back to the original idea, take it in another direction, etc. 70's Pink Floyd was all about creating the atmosphere and reveling in it, and I love the atmosphere of Animals.