Although I haven't been able to play/DM all of them yet, I've read through the WotC Adventure Path modules. My favourites were Heart of Nightfang Spire for its dungeon-crawling goodness with a cool backstory; the other one I liked was Bastion of Broken Souls. Very nice story behind it, and a truly epic feel to the adventure (as it should be, since it borders on (capital "e") Epic Levels).
I'd vote for BoBS as best, but HoNS is a real close second.
note: no experience with non-WotC modules.