Having played the original NR, NR2, NR1999, NR4, NR2002, and NR2003, I can honestly say that I now know how they went from the monstrosity of a simulator that was NR1999 and anything before it to NR4, NR2002 and then to the best racing simulation game available for offline play. NR3 is definitely that missing link for me.
I wish that Sierra wouldn't have lost the rights to making NASCAR games. The EA Sports NASCAR games sucked in comparison to the Sierra release. I really wish they would make new ones, now that EA Sports' contract with NASCAR has lapsed, but now Sierra is focused on iRacing.