Well i would choose the RX7 because;
The Supra can produce much power, but at a high cost, but still can not outhandle a moded RX7
The RX8 has great handling but no power to back it up.
The Sti is on its limits from factory, you cant get much more out of it.
The EVO 8 is alos close to its usuable limits. Yes both the EVO8 and Sti can make gobs of power but its totaly unusable on the road.
Honda NSX is to expensive to maintain, does not have much of an aftermarket. But can handle great.
The 300ZX has a cramped engine bay, but uch potential.
3000GT very expensive to fix, and parts are hard to find.
Skyline, well its a skyline GREAT CAR.
The RX7 combinds awsome handling, lots of poer, great looks, good drivability, and it is quite unique.
But thats just my opinion.