In the end, the point of videogames is to provide an enjoyable experience. Be the game big or small, wholly immersive or quick and surface level, you should enjoy the time that you're playing them. Better games, however, are the ones that stick with you and provide fond memories when you're not there with them.
When I sit down to review a racing game, the questions I ask myself about it are not solely limited to the cars, tracks, upgrades, customization, video, audio, and online play. No, they actually extend to how that racing game comes back to me in the real world. The racing titles I like the best are the ones which, when I'm sitting in my car, have me thinking about racing lines and gear changes, oversteer and understeer, downforce and grip. In recent days, Shift 2 Unleashed has caused me to think about all of that and more. That is to say, Shift 2 is a pretty good racing game and a truly enjoyable experience.
The basic problem I think some people find with immersive racing simulation titles is that people believe that they're better players than they actually are. At its very outset, Shift 2 eliminates that as a possible bone of contention. Before you are actually allowed to begin the career mode, you are put behind the wheel for two races and based upon your performance in those two races, the game calibrates the difficulty level to one that you will find appropriate – neither too easy, nor too hard. The game's decision is, of course, changeable as you go along in the title, but it does provide an excellent starting point.
Ostensibly, your goal in Shift 2, which has you racing on closed courses in real cars, is to win the FIA GT1 World Championship, but I seriously doubt that anyone playing the title actually considers that their goal, it's kind of just a manufactured goal for career mode because career modes tend to need a goal. The actual goal for most people will be to race, to race well, and to do so across the 120 different track layouts (utilizing 35 different real world locales) with a plethora of the 120 different licensed vehicles and then to post good enough times with the game's Autolog system so as to appropriately humiliate all their friends. In short, there is a ton to unlock in Shift 2, a ton to customize, a ton to buy, and a ton of fun to be had, and you're going to want to see and do just about everything the game has to offer.