Temp of a graphics card depends on how well it is cooled and ambient temp.I dont own a 8800GTX, but i can assure you that it's an ok temp.I mean c'mon my 6600GT idles at 63'C and reaches even 100'C (too hot in here)
Those temps are fine, but try googling for coolbits if you want to mess around with fan settings and such. It's an app that unlocks a lot of features in the forceware drivers, with it you should be able to force the fan to 100% and therfore get a few more mhz out of your gpu too.