EA Sports F1 Challenge 99-02
especially with the Sports Car Challenge mod, done by http://www.rsdg.net
There are a ton of other mods, cars, tracks, etc out there too for this simulator..
Everything else is just an arcadish toy compared to F1C and its mods. Period.
Console racing games are more like arcade games compared to this, including the grand turismo series... The level detail, physics engines, race presentation blow anything else out of the water. Even in practice mode, you pull out of your garage in the pits, roll to the track entrance and wait till your turn to go.. And on race day, they truley did give it a "race day intensity" feel. There's communities out there that host online race championships, every week.
Also, in the future, coming soon is the GTR stand alone, and the rForce engine.
Oh forgot about Racer. its an opensource simulator.. probably just as, or maybe even more in depth than EA F1C.. again, there's tons of tracks, cars, setups, etc done by an active community.
Remember, these I listd are simulators... not arcade games..