It is unfortunate that the forza series is only available on Xbox 360, it has great graphics on a small console - the potential on a high rig console is unreal. The playability is great and it makes you want to keep playing even though your eyeballs are burning and your thumbs are stuck in a bad postion. You start off as a new racer and you have to rank your way up from novice driving low spec cars like a ford ka or citreon c1 to a master driving f1 cars. Aswell as driver experience points you have to gain affinity points which is based around car manufacters, For example if you win with a bmw you gain experience and level up just as you would with driver points. You also have a choice of difficulty unlike anything before with assists like abs, autobraking, driving lines, etc. So the driving experience can be anything you want it to be.
Auto vista - is a option of play that allows you to eplore a car in depth with commentry from jeremy clarkson. You can also start the car up and drive it around the track over taking cars - which is a great joy.
The online community of Forza 4 is unreal with the different choices you have, you can either join a car club or start one up yourself. With the online play you can rank up just as you would with single player which helps alot. Especially when you go into single player after online as you have a selection of cars waiting for you to choose. The car selection is awesome to say the least - with every car perfectly detailed. Unlike Gran turismo 6 that uses ps2 quality cars.
You can also make a movie and take photos of your car, this is extremely handy if you have had a mind bending lap as you can show your mates. Then you have the list of group races that consist of groups such as circuit - then you have sub options of the class of car you wish to enter.
Overall the nearest rival to this game is Need for speed the run. Another absolute cracker.