Best driving/racing sim?

What are some good racing/driving simulators for PC that are similar to Gran Turismo?

By similar i mean, vast amounts of cars, parts, upgrades and differant racing leagues...

I dont really care too much about how good the actual driving is but i want a large amount of customizability similar to GT.

Also, the newer the game, the better (id like some decent graphics :D)

note: no NFS games, GRID or Test Drive games.

Thanks in advance.

Look at GTR2 and Race 07.

It has a lot of cars, but you can't customize them in terms of parts. But you can tweak them.

They are pretty much the best sims out there.

But I don't think there is a sim with everything you want.

Burnout: Paradise ıs good.