There are tons of clean Chevelles and Camaros out there,way more than the number of GVR4s out left...the difference is the demand.
The special models like the SS,LS6,Boss,Hemis,etc have always been desireable,albeit not as much so as post Barrett Jackson. They were cool stock,and had racing pedigree. Kids rode their bikes to the dealership to lust after those cars back then. I don't think anyone did that for the VR4...they could barely sell the things.
It's true that the lesser trim level cars are gained serious value,say a 6cyl '69 camaro,but generally its due to the demand to make a SS clone or just a otherwise just clean example to modify. Lots of cars like Ramblers,or weird stuff like '70s Laguna S3,etc were not desireable then,and still aren't as desireable or valuable now either. Even though they are hard to find,other than to a small cult group of people like us with our cars they aren't worth a lot.
The gas crisis killed the musclecar in the '70s,and for years we had to deal with 180hp Corvettes and other anemic shitboxes that wouldnt pull the skin off a rotten bananna. Like a musician that dies before his/her time,it helped seal the legend of those cars. Our cars don't even have that advantage,cars have gotten more and more potent out of the box since '91. The EVO has overshadowed the GVR4,and will likely be the Mitsubishi collectible of the matured fast and furious generation.
Obviously the Syclones,Supras,Evos,3000gts etc were performance cars from day one and marketed to a different demographic,unlike the Galant-not at all suprising they would become valuable. I commend the guys who have the self control to keep GVR4 bone stock and preserved,and IMO it's kinda cool and will make a cool conversation piece someday,but I wouldn't do it with the expectation of making a ton of money in the process.
I'd have to say most folks who have bought a GVR4 (other than when they were new)was for the cheap and easy modding,and for the sleeper appeal. If anything, someday guys will wax nostalgic about launching on unsuspecting Honda at a light or stomping a V8 at the track and how easy and cheap it was to do it than how slow and lousy handling the car was stock. I almost see more of a market for clean period mods like the HKS stuff,VPCs,etc than a stock car.