you can't really base fact on one race I don't think. All drivers have different abilities so whos to say the 34 driver was the best there and if he;d jumped in the STI would have won in that?
I think the GTR would win anyway but I think the best way is for the one driver to do hot laps around the same track, given a warm up in each car to get used to it then go for it. Even then to be fair this should be done over a number a different types of tracks if you want to find out the best overall car.
When it comes down to it though it doesn't really matter as the majority of skyline, WRX, EVO drivers never even make it to the track and generally use them to cruise around in and drag a few people at lights.