Genesis, but a small margin.
Had the Yes run gone from Fragile-GFTO, it might have stood a chance, but that five-album run for Genesis is just too good. I do miss Nursery Cryme, but W&W is one of my all-time favorites.
I'd dare say you could pit Genesis' first 10 albums and Yes's first 10 (both of which go right up to 1980 with two D-name albums, Duke and Drama), and THAT would be quite the battle!!!
-Marc.