Don't like Mazdas? Take it from me, I'm not really a Mazda fan myself (because I try to be a fan of an entire spectrum of cars), but the RE Amemiya Mazda RX-7 from the JGTC is a wonderful race car. True to Mazda, I raced the RE Amemiya RX-7 at Mazda Raceway Laguna Seca, this wonderful race car had wonderful control and took corners beautifully. Maybe not the ultimate Mazda, but this is the car you need if you're serious about taking on the world in your Mazda. This car is awesome. I remember it from Gran Turismo 2, just that the RE Amemiya RX-7 in GT4 has the most recent paintscheme with Aspara Drink (Japan only) as the main sponsor.
To me, this is the best Mazda I've raced in the game from my Arcade Mode experience last Saturday.