I always see people bringing up Wish You Were Here, Dark Side, and The Wall (Comfortably Numb) are their faves -- which is fine -- but as far as Gilmour specifically, Echoes (off Meddle) is his masterpiece in my view; and Fearless is just a fantastic song also. And his work on Animals may be his best next to WYWH. I guess my point is, Comfortably Numb is waayyy far down the list as being his best work -- it's good, yeah, but there are so many other greater songs.
If you don't know Meddle, listen to it -- that's when Floyd became Floyd. One of These Days is still the one song that gets me so jacked up. Waters said it's the album where the band finally learned how to "use" their instruments (after Barrett's departure).
Also, The Final Cut is an album that pretty much was a Waters solo album with Floyd (minus Wright) as his backing band, but there are some great songs on that as well -- but Gilmour's talents aren't showcased much on it (with the exception maybe being Not Now John -- another awesome song).
Point being: check out the shadier stuff other than the popular albums.