Thanks, Leeman. Like PanzerMeyer says. To get your NASCAR fix offline you have the following options:
1) Spend anywhere from 50 to 150 bucks for this seminal Papyrus' last release as pictured above (bought mine a couple of years ago). You do get your money's worth with the plethora of mods available: not just COT, but trucks, Grand National 1970 season, AeroWar88, Winston Cup 1990 season, modern and historical tracks, sound packs (want Chad Knaus to be your crew chief and spotter in one? No problem!), not to mention non-NASCAR mods. The drawback is that the rules are frozen in time (that of 2003 season, yellow flag rules changed shortly after), and though as you pointed out the graphics aged well, it still is no match for the most recent sims. Not many tracks got upgraded past 2005/2006 season if you pay attention to those things like sponsors and such.
2) Go cheap and get EA's NASCAR Sim Racing (saw it bundled with some other EA stuff). It was decent but never really captured me, the cars looked a bit cartoonish and lots of people decried the physics. Not sure if COT was ever created for this sim, it's pretty much abandonware at this point. Might be good for figuring out if oval racing is your thing.
3) Get the TPSCC mod for rFactor (the 1.0 release has the old cars, 1.93 beta has COT but no real liveries, 2.0 is supposed to come out soon with real-world skins), together with a bunch of real-world tracks. Some people swear by its physics, but for me the feel's not quite there yet and I still prefer NR2k3S.
4) Get NASCAR 09 on 360 or PS3. I got mine on 360 and do enjoy it, the graphics (though to some people it's subpar compared to other 360/PS3 releases) and the fact that it's most up to date (though the cars aren't lincensed with the manufacturers, so you will see just a generic COT, no Camrys, Fusions, Impalas or Chargers), although my
Logitech 360 wheel and the game itself are no match for the Momo/NR2k3S combo with mods.
I don't race online but I understand that ARCA Sim and iRacing, though limited in scope (you won't get the COT and current paint jobs) and with some teething pains, may displace, or already have, NR2k3 in this respect. Won't get much in the way of offline racing with them though.