http://www.gtplanet.net/forum/showthread.php?t=162955
GT3 has 289 individual races, GT5 has 126 individual races.
GT4 has 522 A-Spec races, GT5 has 126 individual races.
@ Yamauchi:
Why the fuck did you spend so long on the game and have the cheek to give us less A-Spec races. We don't care about B-Spec. Instead of wasting your time on B-Spec races you could've made more A-Spec races!