Favorite Gameworld: Ganth.
Favorite gameworld from print materials is fairly easy.
I don't care for Dragonlance, don't get me wrong, plenty of cool and neat tings come from there, but I just don't like the world.
Don't even get me started on Spelljammer, ugh ships in space!(Sorry Eric, but yuck)
Dark Sun is another that's fun and has good ideas, but still not my cup of tea.
Planescape is awesome, but it's too big for the limited amount of information you receive.
I really like Ravenloft, amazing campaign idea in my opinion, but not enough supporting materials.
Eberron is a great idea and congrats guys on winning your spot in D&D lore, but still not there.
Mystara is fun but not my favorite. Hollow World falls in here too.
Who can't help but like or at least appreciate Greyhawk, but still isn't my favorite.
My favorite would have to be Forgotten Realms, they have Pirates in a huge sea in the middle of the continent, wars everywhere, ancient flying cities that created a massive desert when they fell, Al-Qadim, Maztica, Kara-Tur, The Horde, Underdark, Undermountain, Drow, Waterdeep, Baldur's Gate, well the list goes on and on. What's not to like? A well designed and thought out map, lots of information available, tons of stories and lore, even the gods got reshuffled with a couple of PC's.