Brennin Magalus said:
Forgotten Realms
CONS: Bloated pantheons of disparate gods that were cobbled together with the skill of a rank amateur; a completely nonsensical geography; a world that is beholden to junk novels; a legion of 2D, overpowered NPCs; Ed Greenwood; magic is too ubiquitous.
PROS: Good product support. However, if WOTC lavished the same attention on Greyhawk, a far worthier setting, Forgotten Realms would become just that.
Wow, looks like someone here actually understands the Realms in all of its infamy.

You have eloquently summed up why I will never play in another realms game again.
As for other worlds, most have been hit already. Kalamar is a great world, very detailed, and a quick readthrough of the books I do own shows its probably THE top-notch world out there. There is a ton of background info (which can be good or bad depending on your view), but unlike the Realms, the background isn't restrictive- its simply a history that can be brought into advantures to give them a sense of context. I haven't used Kalamar yet since my 11 year campaign in my homebrew is still going, but if I were to choose a world to run my next campain in, it would be Kalamar or....
Arcanis:A great world with an authentic and dark feel, this is the world where the flavor text and cultural backgrounds really grab me. Its got tons of cool ideas, from the magocracy of Ymandragore that sends out operatives to "harvest" spellcasters, to the Roman-esque Coryani Empire, to the insidious Theycracy of Carceri (the best evil empire EVER in a fantasy setting), to the yuan-ti goodness of Ssethregore- this world has it all. I'd say its a mid-magic level, well thought out, and has enough material in the main book for years of campaigning. All of the modules and sourcebooks have been good too, although material for Arcanis isn't really prolific.
Finally, there is Midnight. I can't say how much I love Midnight. Its just so dang cool. Its like a Middle Earth where everything went wrong, and the characters are TRUE heroes who don't struggle for money, power, or fame, but for what is RIGHT against all the odds. I would love to run a heroic epic type of game in Midnight, and I just about have my group convinced to do it. The only problem with Midnight is that a lot of gamers don't want to play something dark and gritty, but this is the main appeal of Midnight to me. I have played in a Midnight campaign, and its probably the best roleplaying experience I have ever had.