The Good: Looks amazing, astounding physics model, lots of tracks and locations, a good assortment of vehicle types, toys and unlocks are interesting
The Bad: New Americanized looks is annoying, can't turn those voices off, needs more unlocks, can't upgrade vehicles, not enough event types
Racing games are usually highly criticized because there is an overabundance of them. Everyone quickly pushes out the crappy racers and holds the good ones up high enough so everyone else can see through the overcrowded genre. DiRT 2 is an amazing rally simulator, and I don't think there is another rally racer that does this better. The first thing DiRT fans will notice is the complete visual change from the last game. It uses a lot of elements from GRID and has a more Americanized visual attitude by using real world famous drivers with voice clips to help you out. Gone is the more serious style menus, and I kind of miss those. The virtual menu is pretty neat though which has you walking inside your tour bus for various options, and outside to select your cars. It's a neat idea, but the whole Americanized bad-assery with the drivers is a turn off. Not to mention the voice clips are really annoying to hear over and over again, and there's no option to turn them off.
Once you select a series of events (there are a TON of them) from one of several areas around the world you get to pick your car. Each car has different stats, but you have to buy upgrade packs for different types of events. There are so many different types of cars for Raids, Rally, Races, Trophy Trucks, Dune Buggys, and the list goes on. You can't upgrade your cars (still) but that OK because you can now adjust the settings such as downforce, gear ratio, suspension etc before the race starts (you will have to adjust these occasionally).
You can also select different liveries, rear view mirror toys, and dashboard toys, as well as horns. These are to actually just show off the amazing physics engine, but it's neat to see a toy dangling around in real time physics on your dashboard and mirror. Once you hop into a race you'll notice the superb cockpit view that was revolutionized from the first game. Everything can be seen and not just your hands. You can look down and see your foot moving on the pedals, your hand shifting, and all the switches and parts of the interior. You can even see your screen swaying on your left in the Raid cars. It's astounding how Codemasters got everything so detailed without having to have some sort of ultra crazy hardware requirements.
When you're actually racing everything comes to life with the physics and sound design. You can hear rocks tinging off your car, dirt scraping under your tires, water splashes up on the windshield and your wipers kick in and wipe it off. It all looks amazing and adds to the realism. Your car will get damaged in real time and dirt will stick and cling to the car as you drive. Depending on what difficulty you chose you can view your replay at any time and rewind time which was borrowed from GRID. This helps a lot during tough and long races. Sliding around and drifting around corners is all about skill and that's what's so great about DiRT 2 is that you win based on your skill entirely. The AI is also great since they will crash and go crazy when trying to catch up to you, they may even get totaled and have to drop out of the race all together.
You never really get bored with the game because you're always leveling up from your XP you earn in races (even completing "missions" such as jumping a certain height etc.) and constantly unlocking new tracks, locations, and different event types. DiRT 2 also supports Windows LIVE and the Xbox 360 controller which is great for people who love that. I want to give DiRT 2 a perfect score, but I wanted more than just racing type events, and the sudden change in style really bothered me. I also wanted to be able to actually upgrade my cars, and have more toys, liveries, and unlocks. There's a very small amount and that's a little disappointing. The game can also be very hard thanks to such realistic physics where you'll be retrying some events 20+ times to get first, but if you drop your difficulty too much you won't earn much money.
I highly recommend DiRT 2 for rally fans, racing fans, or anyone just loves simulators. There's enough here to make fans of the last game jump for joy, but some of the sudden changes will make them grumble in annoyance.