rotary is a different beast, now for apples and apples, comparing a ferrari motor to a 7m..... their rod to stroke ratio is critical in a high revving motor, Dont think its JUST THE STROKE cause its not, it comes down the rod/stroke ratio, rb26 like to rev, b16 honda motors like to rev(actually they have the closest to perfect rod/stroke ratio, still not a honda fan though) The biggest reason I see is the fact that the actual speed of the piston is slower on these motors at certain critical points of the combustion process, if you research it a little more, someone can explain it alot better than me. Throttle responce would come from efficiency(lightweight, low friction materials, hi compression, etc...)
EDIT: just buy a lotus or an s2000 and call it done.