Echoes. That's the primary reason it ranks so high. Plus...One Of These Days, Pillow of Winds and Fearless.
I like Seamus, it's a lark and I don't mind a sense of humor now and again, sure is more fun than anything Waters would contribute post-77.
Any of those albums could change order depending on what kind of mood I'm in. When I first did the list I thought about having WYWH and Meddle tied for first place, but then I just flipped a coin in my mind.