What is it?

Carmageddon is a must. Not a racing game as such, but still fun.

It's no longer on gOg: Colin McRae Rally 2005

Flatout 2.

Motoracer and Motoracer 2 are quite good. Motoracer 3 gets a bit too arcadey for me, the amount of sliding around that goes on is just ridiculous, even for an arcarde racer.

GRID ;)

I'd say Flatout but that's more track & field than racing.

That seems to be the winner by default. :) Decent racer too!

yes, it probably is but, sadly is also not the best version of it out there - Flatout Ultimate Carnage is Flatout 2 HD with more content and NOT on GOG - sucks!

Jack Keane 2:Hot Pursuit

I'm surprised at how limited that racing catalog is. :o

A lot of the games run into licensing issues as a result of them using real cars. They opted to license the cars, but not to get a license that covered the game in perpetuity, which means that GOG or somebody would have to get a new license with the automakers where applicable.

I can only recommend GRID....and write it for the x-time: We need more racing games GOG

Ah, basically what Telltale and Activision + Marvel do. I never understood that logic.

Monster Truck Madness! Oh wait, that's not in the catalog, so nevermind......

POD GOLD is definitely a worthy title in the racing genre. To be honest, it's as simple and weird as a racing game can get, and the storyline kind of sucks. But holy nuts, is it ever fun to play if you just want to get out and race. You also get a massive variety of tracks and cars, a full damage model, and complete vehicle customization that allows you to fine-tune your car.

Also, as user hedwards above said, I'd recommend the Moto Racer games.