Think GRID is too arcade-ish, then try this deep simulation of the sport of GT Racing!
Another complaint I've heard is how it is too easy to drive the cars, though they probably never turned off the traction control and other assists that are there to help people new to simulations. There are also alternative physics setups you can get (also for free) to suit just about any taste, from casual to hardcore. Speaking of download-able content, this sim has an immense amount of it. Since its release, modders have been making nearly every aspect of racing available to download for free, including- tons of cars/tracks/textures/graphical improvements and even race types not intended in the release (like Formula 1 and even lawn mowers!). Many of these mods rival anything done by commercial companies, and sometimes surpassing anything that -could- be done cause of licensing issues that a company looking to profit would have to go through. There are just too many things to mention about this sim to go through here, but suffice it to say, its worth your $20 (or less) if your a simulation fan that doesn't have it yet.
A few great features are: Most real flag rules apply- great training regime for those new to simulations, or people wanting to get into real life racing- tons of customizable commands (great for those with DFGT steering wheel cause of all the buttons available)- possibility to preset your pit stops before a race with fuel amounts/tire types/etc- changeable weather and night/day cycles (in 2005 it had this!)- tons of free mods- huge fields of cars (more than 40 at once)- and, people still play it online every day (a testament to its longevity). In short, plenty of content.
In conclusion, if you were tired of all the racing "games", and wanted something more realistic for a bargain price, its hard to go wrong here. Just make sure your willing to invest the time it takes to learn the sim, and the sport of GT racing. If graphics matter more than realism, then stick to GRID, which is a fine game for casual racers looking for a short, quick fix of speed.