I think tiny sport(y/s) cars such as the Z3, S2000, MGB GT, the new MR2 roadster, and even the Miata look good only as convertibles. The hardtops are just so bulky and awkward...
Some of the bigger sports cars like the Vette, Viper, and 911 look awesome as coupes... Not the little guys. I'm a big fan of coupes.