It was obvious when Firemint released Real Racing 2 late last year that the iPhone- and iPod touch-only game was good but unfinished—an early example of how highly detailed 3-D car models and backgrounds could look on Apple’s new Retina Displays, with caveats. On the plus side, Firemint included 30 licensed cars ranging from low-end Volkswagens to tricked out Lotuses, plus 15 entirely different international tracks, and some seriously…