The GT4 version is definately pretty close, but again, physics... well, the physics are definately not that great. I haven't played the full version in PGR3, but the GP version looked and felt pretty good. I put that game down though, since it looked good and all, but just didn't do it for me in the realism sense.
*edit: that rFactor version makes me want to try it out... even though I laid that game to rest ages ago.