Skyking...
Think of it as the difference between Microsoft Office (the 1st
one),office 95, 98, or 2000 & XP.
you can have NR(1), NR2, NR1999, NR3, NR4, 2002, 2003. but what is neat is
that you can have all of them (I still have 4, 02, and 03) on the same
machine separately but only because I haven't got 2 copies of NR03 so we
can race on a LAN I have at home with friends, and I keep putting off,
removing NR4.
they are all different. up until 1 month ago, you could race NR3 online
with others, but plug has more or less been pulled. I haven't checked but
few prolly run nr4, and might be a few doing NR02, but you cant race those
of us running 03 without having 03...
particular difference's, well it would be easier to have you read papy's
site, I think, where they tell you what is new for the version your looking
at (selling points?) Physics are different, some controls and a few other
things have been adjusted and stuff... 03 doesn't just update 02. Lot of
things that changed are really nuances (spelling?) that make the game seem
better (some say worse?) so your mileage may vary.
hope that help.