The smaller the motor, IMO the better the mpg should be. I use to get 35+ mpg with my old civics, the RX8 motor I'm guessing is around a 1.3L while it makes good power for it's size, it still leads the market for worst MPG in its class. AS WITH worst power its class, people will argue that it is a "special" car since it has the rotary motor, being that it's 2008 and fuel is 145 a barrel, I could care less if it's a cool design, bottom line, the car needs more power, or better mpg. at the very least a turbo should be on it.
MR2s are very nice cars, RX8 is a very nice car to drive.
350Z is pretty high on the rankings handling wise, just behind the S2000. Thankfully with very little work the 350Z is able to handle like a dream.
I do agree, size/power the rotaries are nice, but in the end an S2000 will spank the RX8 all over the place, even with the larger (more heavy) motor. =)