Well, first off I'm cheating a little here, cause I wasn't here the entire time, but from all I've heard, here's my rating:
60's KRUX
70's KDKB
80's KSLX
90's KOOL
2000s KCDX
KRUX based on some of the old airchecks I've heard, the announcers they had, and what I've heard from people who lived in the valley during that time period.
KDKB had a 24% share of the audience at one point in the 70's. They owned the rock market and could do no wrong for most of the 70's. I heard a few airchecks, from that time period. KDKB ruled. Their longevity with the format is pretty amazing too.
KSLX when I first heard them in the 80's was fresh, because Classic Rock was a new format. They were true to their format. There was 1700 songs in their library when I was there, which is pretty decent by today's standards. They had a great morning show, one of the best I've heard with Jones and Boze, and were firing on all cylinders.
KOOL had a great airstaff in the early 90's. They had competition from Sunny 97 (now Mix 96.9) at that time, but KOOL was #1 in the market. They had personality, a high energy, fun staff, and perhaps Oldies radio was also a bit fresher in our minds too. Their promotions were top of the line, and everybody loved KOOL, and the image of the radio station was top notch.
KCDX because they actually real variety, which to me outweighs the negatives of hearing some real oddball songs that don't completely fit the format. Most radio stations have lost their appeal over the years due to shrinking playlists, in my opinion. It may be unfair to list KCDX because they aren't a true commercial station, and don't have to worry about ratings, and they don't play 8 minute blocks of commercials during afternoon drive, but no other stations have really captured me in the last 10 years, unfortunately.