Gran Turismo 5 is probably the best sim racer out there, but a few really annoying issues stop it from being perfect.
Presentation
For a start, the menus of GT5 look nice, but when it comes to actually using them, you immediately realize that they are deeply flawed, and annoying to use. This coupled with terrible loading times means GT5 is off to a bad start! The graphics of the 200 odd "Premium" cars are unreal, or, to put it more accurately, real!The graphics of the "standard" cars and the tracks however, are sub par, but they're good enough. The damage model, even on the permium cars is lame, but the sound effects and engine noises are fine, with the ability to use your own music a fine addition considering the poor music already on offer.
Cars/Real world Tournaments
As I said before, the game features over a thousand cars, but as most of these are family cars, you aren't likely to want to drive them. Some of the real world racing series include a faux World Rally Championship, Le Mans Series and Formula 1 series, and licensed but not fully featured Super GT and NASCAR championships. There are many classic Sports Prototypes in the game, but unfortunately, they all cost ridiculous amounts of in game cash. On the road car side of things, there are many past and current hyper cars to go with the crap.
Career Mode/Story
In the career mode, called GT Life, you have to work your way through various championships, earning experience to unlock more tournaments, and money to spend on cars, all fairly unoriginal, starting with small family cars like the Honda Civic and Toyota Yaris and moving to faster cars from there. An interesting feature is the B-Spec mode. In it, rather than drive the car yourself, you coach another driver to do it for you, like a crew chief. Although this may sound fun, believ me it is not, and the fact that most races are twice as long as normal doesn't help.
You can buy upgrades for your cars, anything from new tires to turbo charging to an aerofoil, and you can tune almost every aspect of your cars setup to the finest detail.
Game-play
GT5, depending on what assists you turn on, plays anything between semi-sim and full simulator. The AI drivers, even on the highest difficulty are kinda stupid and will stick to their line most of the time, never really making mistakes. The game does feature pit stops, but you'll never really need them until the endurance races latter in the game.
Multiplayer
The multiplayer of GT5 is really quite good, since most people want to race rather than muck around, but unfortunately, the match finding feature is shocking, making it hard to find the race you want.
All in all, the good far out-weigh the bad in GT5, so if you haven't already done so, you should defiantly get it.