$21k in 1990 or $22.5k in 1991 (when model years 91 and 92 were released) works out to about $34-35k in 2009 dollars.
Here
The Evo X MR or Subaru STI is probably a pretty good comparison point in terms of features and price. It was a top-of the line sedan with the highest Japanese car technology of the time.
The VIN on the VR-4 even carries the "Premium" model designation.
Another good benchmark is that the VR-4 had about the same MSRP as some of it's competitors, the low end BMW 3-Series (318i - $21k) or the Audi 80 ($22k, equivalent to a modern A4)
With all of those as benchmarks, you're looking at about a $35k-$40k car in today's market, once you factor in all added costs from safety and emissions regulations.
With that range as a benchmark, you would be looking at a fully loaded Evo X GSR or a base Evo X MR, a fully loaded STI, a low to mid-range Audi A4, or a BMW 328i/335i/135i
Quoting slugsgomoo:
except that car prices are outpacing inflation pretty significantly.
I think you have to look at the other models in the class (like the top of the line FWD galants) and compare them to where they are today.