The 3000GT VR4 is right out. Its AWD system is fairly simple and maxes out at 50/50 power distribution, it's got a heavy drivetrain, and it's transverse so its weight distribution isn't great. Like JonB said, its front end has to do a lot more work for less benefit. It makes 1 more hp and the same torque as the Supra, but its torque peak is much lower- 2500rpm vs 4000rpm- meaning all of its advantage is used up at launch. Once things pick up, it's in the dust with its weight at the wrong place and its torque declining.
Really the race is between the Supra and the 300ZX. The Supra is just a bit lighter than the 300ZX Twin Turbo 2+2, and it makes 20 more hp and about 30 more ftlb of torque. Also, the Supra has a sequential turbo setup, meaning it gets a double surge of power, across the rev-range. The 300ZX used parallel turbos, giving it a more traditional turbocharged power curve. Super HICAS 4-wheel-steering and an expensively developed suspension and chassis seem to give it an edge in cornering, but the Supra will take off on straights. Where the 300ZX looks like it will really lose out is brakes- the stock units are not enough to stop its nearly 2-ton mass quickly.
So the Supra takes it between those three. But what about versus the other super-sport of the early 90s: The RX-7 Twin Turbo?
The RX-7 Type R has about 60 less horsepower than the Supra and 100ftlb less torque, but it weighs a full 500 pounds less with the best suspension to come out of Japan in the 1990s. In a straight line, even the Mitsu will beat the RX-7, but take it into any corners, and that rotary will shine. It also has a twin sequential turbocharger setup meaning its power delivery is more constant, even at lower revs around a corner.
Moving on.
In a race between a Celica Supra, an MR2, a Corolla GT-S, and a 200SX, the Supra will take it. Although not quite as capable in the bends as the other 3, it has more power and torque, and a competent enough suspension (in a relatively-low speed race as it'd be in) to save time in the corners. The MR2 is easily the lightest of the three and slightly more powerful than the GT-S. The 200SX becomes the weakest link. It's the second-heaviest, with the weakest suspension, and the worst delivery of power. Unfortunately, Nissan didn't develop it to be a great racing car- they had the 300ZX for that. The S12 would be competition for the Corolla GT-S, but the MR2 and Celi-Supra would be running circles around it.
IvDave, I think if I was buying an entry-level sport coupe in 1985 (take the Mustang SVO off of there- it was more expensive than the GT) I'd probably end up in the 200SX. It's not the quickest-cornering or the most powerful, but it has a good balance I dig. It'd be that or the Corolla GT-S, which is lighter and more fuel efficient. Gas was disproportionately expensive in the mid-80s.