By far, "Nascar Sim-Racing" by EA Sports, and EA Sports--"Need for Speed Undergournd 2". Basically, anything by EA Sports is real authentic and they make the best sims.
The sim racing version includes all these specs:
New Realistic NASCAR Physics: Extensive test driving by NASCAR drivers helped bring home the true-to-life feeling of 190-plus MPH racing.
New High-Definition NASCAR: 29 high-resolution dynamic tracks and 3D audio deliver the roar of V8 engines.
New Telemetry Analysis: Analyze car setups and your best laps, then compare your times against those of real NASCAR drivers.
2 New NASCAR Racing Series: The NASCAR Craftsman Truck Series and the NASCAR Busch Series join the competition.
All-New Career Mode: Start from humble beginnings and battle your way through NASCAR's minor leagues to make it big.
The Definitive Online Racing Experience: 43 online players race live on the same track. Featuring a Ranking System, Hot Lap Leagues, Tournaments, and Voice Over IP, online racing reaches a whole new level.
New Replay Studio: Replay entire races, your greatest Hot Laps, or favorite racing moments, then save ‘em all to view later.