Core i7's are already powerful enough to play most games that will be developed in the next few years. It will be a while before games are optimized to use more than 4 cores, but that day will come. The hyperthreading on the i7's should help fill the gap, even though they will never be as powerful as additional cores (1 core w/HT < 2 core). I decided to get the i7 860. It should help it last longer as an acceptable processor for most games.
List of Quad Core optimized games.
Note:It is important to note that these games offer a serious performance increase when upgrading to a quad core from a dual core,and not from a triple core.
Football Manager 2010 (unconfirmed)
HAWX (confirmed)
Battlefield Bad Company 2(confirmed)
Supreme Commander(confirmed)
Supreme Commander Forged Alliance(confirmed)
Supreme Commander 2(confirmed)
Resident Evil 5 (confirmed)
Prototype(confirmed)
Grand Theft Auto IV(confirmed)
Left 4 Dead(confirmed)
Left 4 Dead 2(confirmed)
Far Cry 2(confirmed)
Dragon Age:Origins(confirmed)
Flight Simulator x(confirmed)
Devil May Cry 4(confirmed)
Lost Planet(confirmed)
Lost Planet 2(confirmed)
Company of Heroes series(confirmed)
World in Conflict(confirmed)
Medal of Honor Airborne(confirmed)
Call of Duty World at War(confirmed)
Call of Duty Modern Warfare 2(unconfirmed)
ARMA 2(confirmed)
Stranglehold(confirmed)
Empre Total War (patch 1.3)(unconfirmed)
DIRT(unconfirmed)
DIRT 2(confirmed)
Brother in Arms: Hells Highway(confirmed)
future Source Engine games(confirmed)
future Unreal Engine 3 games(confirmed)
Unreal Tournament 3(confirmed)
GRID(confirmed)
The Sims 3(confirmed)
Anno 1404(confirmed)
Batman Arkham Asylum(confirmed)
Shattered horizon (confirmed)
Red faction:Guerrilla (unconfirmed)
Assassin's Creed 2(unconfirmed)
Tomb Raider Underworld (unconfirmed)
The Last Remnant(unconfirmed)
Aliens vs Predators (unconfirmed)
Operation Flashpoint 2
ragon Rising (unconfirmed)
Prince of Persia (unconfirmed)
http://www.grandtheftpc.com/2010/03/list-of-quad-core-optimized-games.html