My ranking would be Turnberry & Prestwick followed well behind by Troon and Western Gailes.
I've only played each once, and Turnberry twice on the same day. I haven't seen many elite courses but Turnberry is in my top 3-5, however as previously said mostly for the seaside holes (although I love #s 5, 16 & 17. The opener and closer do little for me.
I love Prestwick, quirk and all. On Rich's "Member" thread, I'm not sure what he means but I could happily play Prestwick every day from now on.
Troon had a few more memorable holes for me than WG (though I loved 6 & 7 at WG), but neither course stood out. They were both early in my trip, and I sure didn't play well either.
Frankly, once around a course isn't nearly enough for me to take it all in. But whenever my next trip to Scotland occurs, I won't even think about hitting the west coast again until I can visit the Muirfield area and northern gems.