When the Z32 was in production the Skyline was Nissan's flagship car....period. Plus I'm going to agree with the apples to oranges comparison made above. The US and Japan markets are completely different. The 240SX was never a sports car. The Silvia was a sports coupe. In countries that didn't get the Mustang, Camero, and Firebird, Nissan could afford to foot a low end sports coupe alongside it's high-hp sedan (Skyline) and sports car (Z32). The US market has always had the 240SX as a 5 seater coupe...nothing more. In addition, Nissan's current strategy is to develop more platforms in order to compete with Honda and Toyota. To paraphrase Ghosen, people who buy a Honda or Toyota aren't necessarily looking to buy those cars when they do. Most people who buy a Nissan had the intention of buying a Nissan in the first place.
"The 300ZX Turbo is a dance; it's a song; it's rolling, roaring automotive art. There is no color that doesn't suit it. There is no mood-lifting chemical substance it can't replace." - Automobile Magazine