Not counting the racing versions:
1. NSX-R '02 (Can be bought new)
2. NSX-R Concept '01 (You can only win it)
3. NSX Type S '01 (New)
4. NSX '01 (New)
5. NSX Type S Zero '97 (Used)
The fastest racing version is Honda Takata Dome NSX '03, second fastest is Honda Mobil1 NSX (JGTC) '01
The data is from Famine's Trail Mountain times spreadsheet.