Personally for me, Civ 5, Deus Ex, and Witcher 2 are top of my list. Recent video/gamplay vids of Witcher and Deus Ex are slowly solidifying them as front-runners, but you can't go wrong with Civ, especially with hexes and ranged combat.

This is my to buy list. These are already preordered where available in the "best" edition possible, for example WoW:Cataclysm collector's edition.
PC: Civ 5, Amnesia: The Dark Descent, WoW:Cataclysm, Diablo 3, Shogun:TW 2, Torchlight 2
PS3: Fallout:NV, Arcania, The Witcher 2, Mafia 2, NHL 11, FIFA 11, Castlevania:Lords of Shadow, Medal of Honor, NFS:Hot Pursuit
That's off the top of my head. With all the great releases this fall I don't really have a perspective beyond the coming christmas.

I'm looking forward to Amnesia: The Dark Descent, though I'm not giddy with anticipation. Trine 2 and Torchlight 2 have me tentatively interested. Other than those few... I can't really think of any. It's been ages since I've really been excited about an upcoming game.

WoW: Cataclysm and DoW2: Retribution.
Nothing more.

For me it is Call of Duty: Black Ops, Need For Speed: Hot Pursuit and at the GamesCom I saw at the Kalypso booth an interesting game called "The First Templar"

Civ 5, Mafia 2, The Witcher 2, Dungeons, Jagged Alliance Reloaded, City in Motion.

Looking for The Witcher, Fallout New Vegas and mostly The Last story, hopefully it's gonna get realesed soon

Fallout: New Vegas
Dead Rising 2
Dawn of War 2: Retribution
Gray Matter
Lucius
Dungeons
That's all I can recall right now.

Civ5 and WoW:Cataclysm and maybe deus ex but I want to see some reviews, gameplay vids or something like that before deciding if I want it or not.

Garshasp(first Iranian Indie game which will reach international foot, gotta see what happens there)
Lucius
HL2EP3 (LUL)
Duke Nukem Forever
Gray Matter
Witcher 2
Amnesia (Pre-ordered,yay)
Fallout Vegas
Batman Arkham City
Darksiders PC edition
Alice: Madness Returns
Portal 2
Metal Gear Raiden
Despite Ubisoft I really can't wait for Beyond Good & Evil 2.
I personally hope there will be PC port of Bayonetta, I really want to get my hands on this one.

hmm
xbox: AC:Brotherhood, NFS:Hot pursuit
PC: Civ V, Civ V, Civ V!!!

Shogun TW 2 (hoping that the smaller scale will make it easier to manage, Empire feels as much a chore as a game at times)
Fallout New Vegas
Civ 5
DoW2 Retribution
Warhammer 40000 Space Marine
Mafia 2
Gears Of War 3
Thats about it for the relatively short term

Men of War Assault Squad is looking awesome.
Though, sadly very little news coverage of it :-(

Witcher 2
Fallout: New Vegas
Deus Ex 3
Mmmm... Sequels

Jagged Alliance 2: Reloaded
Jagged Alliance 3
Civilization 5
Dungeons
Tropico 4
City in Motion
MUD TV
Torchlight 2
Nancy Drew: Shadow at the Water's Edge,
Nancy Drew: Secrets Can Kill Remastered
HoMM6
In more or less that order. ;)