Yep, it's hard to choose a favorite in their catalog, and I agree with your picks as well. Shine On You Crazy Diamond, to me, is probably the greatest song every written / performed. That song, and Welcome to the Machine, is why that album is at the top of my list.
Yep, really hard. Just shows how mesmerizing their catalogue is. I see your point, those two songs are absolutely top-notch.