Nowadays it's mostly sims, currently mostly Assetto Corsa (also own rFactor and have played it quite a lot, although that was some time ago). I have spent quite a few hours in Euro Truck Simulator 2 as well, it's surprisingly addictive.
Back in the days there were quite a few other games though.
Chicago 90 (PC, 1988), escape from the cops. Small but sweet game.
Stunt Car Racer (PC, 1989), I played it on Amiga at friends and later on my PC (it was available for almost all formats back then though, C64 etc). Looking at the wiki page I just realized it was made by Geoff Crammond, who made the great Grand Prix (well, and the earlier GP, haven't really played them though).
4d sports driving (PC, 1990) was some good fun, crazy tracks and some cool cars.
Test Drive III (PC, 1990), awesome open road driving.
Car and Driver (PC, 1992), another awesome game with great cars and racing both on tracks and on large open roads.
Need for Speed (PC, 1994), probably still my favorite in the series, might be the filter of nostalgia though.
Gran Turismo (PSX, 1998?), hours of fun with this one, including memory card battles. Also played quite a few hours in 2-4.
Grand Prix 4 (PC, 2002), excellent F1 game.
Richard Burns Rally (PC, 2004), the best rally game/sim ever, a game I have actually bought again recently (well I never owned it before cough), haven't gotten around to yet. It's still got a huge following and active mod community.
There's been a few more, some modern Need for Speeds (Underground, Pro Street, Most Wanted), one of the Tocas (the first?) etc, but many of these early ones are associated with some good memories for sure.
You can probably tell I'm a PC guy, and has been like, forever