The benchmark for performance is the (last gen) Porsche 911, so for the money, in a new or new-ish car, nothing really.
Less torque (and as specs will reveal less actual braking and cornering performance) but similar good looks and style: FR-S and MX-5.
EDIT #1: And, to be sure, some serious fun factor for those two ^^^
Likely competitor, but less refinement and worse performance: Genesis coupe
Rally car version of sports car (4-doors... bleah): WRX and Evo.
After that, we're into muscle car striving to be sports car territory, where if you invest some bank, you can have a real beast of a car that can even turn and brake (e.g., mid to top grade new Mustang et al), but for a more conventional "true" sports car, there really isn't anything else on the market at this price point.
And frankly, the 370Z spanks the 350Z in every performance metric and in refinement, so I wouldn't even put it's predecessor on the list as a real rival (Edit #1a: and the newest MY iteration is now at least 7 years old... by "new or new-ish" I mean "less than 5 years old".)
http://fastestlaps.com/comparisons/n...ssan_370z.html
Edit #2: I am a huge fan of the Z4, one of the only Bimmers I have any real affection for... but it's a lot more money...
