it depends which aspects of gran tourismo you are looking for. if you just want the massive selection of cars then i would say test drive: unlimited. if you are looking for a great simulation look into
www.liveforspeed.net. if you want a good balance of both then GT Legends might be your cup of tee. just be warned, any good simulation on the PC will require a good steering wheel to be competitive.
my next purchase will most likely not be a racing game. if medal of honor: airborne releases on schedule (august 30th), i will once again be roaming the streets of europe in the 1940's.
most of the big hitters aren't due until sometime the 4th quarter of this year and the end of 2008, which is also when i suspect crisis will be coming out. i fear it will be a bit to resource intensive for the average joe for them to risk a release in 07. with all the new hardware coming out at the end of 07 it might be a smart move postpone the release to at least the end of the 4th quarter of this year.
some of the big titles to look forward to:
GTA 4 - 2008
Call of Duty 4: Modern Warfare - 2008
Starcraft 2 - 2008
Alan Wake -2008
Operation Flashpoint 2 (the real deal - non of this ArmA BS) - 2008
Fallout 3 -2008
Deus Ex 3 -2008
Assassins Creed - november 2007
Splinter Cell: Conviction - 4th quarter 2007
Age of Conan: Hyborian Adventures - october 2007
Kane & Lynch : Dead Men - 4th quarter 2007
Crysis - september 2007
Half-Life 2: The Orange Box - 4th quarter 2007
just to name a few... yeah, i am bored.