Indycar. It’s been more than 25 years since Papyrus’ « Indycar Racing 2 ». Nothing since then that really simulates the rules and offer that unique mix of road courses and oval tracks.
Sadly, I can’t see this happening. Indycar is all but ignored by the general public, with the exception of the Indy 500.
I think more people know about Indycar than know about GT3 racing.
For me it has to be Indycar, the mix of circuits and the cars would make it such an interesting game. On top of that, a historical mode with the 90s cars would really take it to the next level.