I must admit I have only really discovered Animals quite recently but have been very impressed, the three main songs are all great and work together extremely well. I'm also fond of the two halves of Pigs On The Wing, I do agree with Roger Waters that the album needs that light at the start and end to contrast with the rather dark material making up the bulk of the album.
If I had to pick a favourite from the album I'd go for Sheep, I love the piano introduction and the lyrics are very cleverly written with a strong secondary political point aside from sheep = the masses (i.e. that revolutions only result in a slightly different version of the status quo, a few sheep become pigs or dogs but the rest remain sheep and still have to do as their masters tell them). The imagery here is powerful too, when I hear the middle section I imagine the sheep being taken to a slaughterhouse while the line 'wave upon wave of demented avengers march cheerfully out of obscurity into the dream' creates a fantastic picture of the sheep revolting.
Although Roger Waters does dominate Animals to a greater extent than the earlier albums, I still feel that Animals is a collaborative Pink Floyd album - Gilmour shines on guitar (and on bass) throughout the album, Dogs features some of his finest work and the squealing pig talkbox on Pigs is genius, while Wright's piano and synth are strong, especially on the introduction to Sheep. Also, it is impressive that music of this sonic depth was created by juts the four band members, I do love The Wall but it's definitely the sound of Waters with Gilmour and session musicians, rather than Floyd working together as a band.