Birthright 11
Blackmoor 23
Council of Wyrms 6
Dark Sun 31
Dragonlance 8
Eberron 23
Greyhawk 24 Lots of things to appreciate, but for me it never sparked the desire to tell new stories
Jakandor 17
Kingdoms of Kalamar 18
Lankhmar 24
Mahasarpa 18
Mystara 26
Pelinore 5
Spelljammer 18 One point for chutzpah -- I never played it myself but some of my close friends had a blast.