Gran Turismo series have always been about the huge number of cars and incredible detail. Since the release of the excellent PlayStation 2 exclusive Gran Turismo 4 in 2005, Polyphony Digital had five and a half years to make its successor even more impressive. And guess what? They did. You can see that in the Photo Travel mode, especially the night scenes, where you'll be astonished by the perfectly rendered, photorealistic car models and wonderful light effects.
When you drive a car, the experience is equally as impressive. As "The Real Driving Simulator" slogan says, you'll be impressed how realistic the driving experience is.
Gran Turismo 5 is said to use the full potential of the now outdated PlayStation 3 hardware. And it can be really jaw-dropping at times. Unfortunately, not the whole game looks that good. While city tracks and most professional racetracks look incredibly detailed and very interesting, the same can not be said for the Top Gear Test Track. It's just a runway, a plane, a filming studio, and that's about it. Not to mention the incredibly annoying invisible walls. The game is capable of running at 1080p resolution at stable 60 frames per second, which not many PS3 games can brag about. However, in order to maintain a stable framerate on a limited hardware, Polyphony had to skimp on motion blur and some other technologies, which resulted in poor sense of speed - when driving 200km/h you'll feel like you're driving 100km/h.
As always, Gran Turismo 5 possesses an unbelievable number of cars - this time it's 1001 by default, but the number can be extended via paid DLC and free patches, which brings the overall number to about 1090 (as of January 2013). However, since cars need to have more detail, they wouldn't all fit, not even on the Blu-Ray disc with massive 50GB capacity. Because of that, the cars are split into two categories: Premium and Standard. Premium cars are built out of 400,000-500,000 polygons, which makes them look incredibly realistic. They also have detailed interiors. Standard cars are only upscaled versions of the cars from Gran Turismo for PSP, and they have only 15,000-20,000 polygons and drastically less detailed interiors. There are about 290 Premium cars, and the remaining 800 are of the Standard class. For the first time ever in Gran Turismo series, cars have visual damage modelling. However, the damage is so slight it's almost insignificant. While hitting the car into a wall at 300km/h in real life would probably cause the whole front half of the car to be destroyed, in GT5 it would cause only a slight polygon shift and a bumper falling off if we're talking about a Premium model. Luckily, the damage is not only cosmetic but mechanical too, and you will notice that the car loses control more easily when damaged. There's no way to "total" the car like in GRID and NFS Shift, though, which negatively impacts realisticness.
Gran Turismo 5 offers slight customization for most cars. You can modify its performance as well as its looks. You can place spoilers, replace bumpers and change wheel rims on a car. You can also change the body color and rim color on a car. And there, we come to one of the most annoying things in the game - to get a new paint color, you must buy a new car. So basically, if you want that cool Lime Green color, you must spend 375,000 Credits on a Lexus LFA (which is the only car that sells in that color). When you buy it, you get a Paint Item that you can use either to paint wheels of a car or the body of a car, and only once. I once found myself buying 5 Lexus LFAs just to get 5 Lime Green colors. Incredibly annoying.
One of the more interesting innovations in GT5 is the Course Maker, which lets you create your own racetracks. Compared to other track creators (like Ridge Racer Unbounded), the Course Maker seems quite limited in features, but it's not bad by any means.
Photo Travel is an interesting mode where you can take your Premium car to many interesting locations such as Kyoto or Red Bull Hangar and take spectacular photos of it. The photos look great and can have a resolution up to 3840x2160, which is rather impressive. You can export those photos to the hard drive on your PS3 and copy them to a USB if you want to.
Racing in the game is quite an experience, despite the poor sense of speed. You can race against up to 15 opponents at a time. The opponent AI isn't too bad, but it's nothing special, just average. There is also a B-Spec
The conclusion is, Gran Turismo 5 is a very good simulator that has some flaws, but they are outnumbered by its advantages. I think it's definitely a worthy successor to the Gran Turismo 4. GT4 was great, but it seems quite limited in features once you play GT5, which can only be a good thing.