I think it's the S2000 hands down (vis a vis feel and mechanical engineering). I've owned several S2000s, and still have one now.
I've gone through a 08 STi, 11 G37S, and a 11 Evo X all in the pursuit of having a daily drivable car with a similar feel and fun as the S2000.
I've wanted something with four seats in case I have some extra passengers, livable creature comforts, and quiet cabin, while at the same time offering near 50/50 weight distribution, rear wheel drive with an LSD, and a fun high revving NA engine (all characteristics of the S2000, and to me, the definition of a sports car).
After all the gyration, the M3 is the final answer. I've sworn off all wheel drive turbo machines for the foreseeable future.