Here is my take man.Broke into point for ease of use.
If you have played any gt game you pretty much know what to expect as they add some nice things, but overall it feels like gt.Good points
The game has moments were it is hard to tell real life versus photo mode. The graphics while actually playing are amazing at times as well.
The feel of driving is the closest to real life I have ever played. I have the dfgt wheel so this helps a ton, also never played any of the pc race sims so take that into consideration.
If you have played any past GT game the ai is very much improved
The amount of cars in the game is crazy
The special events are super fun and crazy hard at the same time Nascar training type stuff staring a zombie like Jeff Gorden rally training type stuff with and without Sebestian Loeb and ton of crazy/random/ or specific challenges
karts which sounds fairly lame and I thought would bring nothing are crazy fun to drive FYI they are not what most think of when they here karts top speed is about 85mph or so
A ton of stuff to unlock(weather,damages to car, other stuff I can't think of because I am up too late) by playing specific challenges or getting driver level high enough. I like this it helps keep game fresh and difficulty is more manageable by providing a more gradual climb. Some hate it so could be a bad point to some.
If you like take pics photo mode is awesome. Somewhat overwhelming to me atm, because I don't have much experience with cameras etc. Link here to some peoples awesome shots normal folks took using it. http://www.neogaf.com/forum/showthread. ... 35&page=16Bad points
it can be inconsistent some weather effects/smoke/dust cars a odd pixelization (blocky) at the edge of cars at times.(they are reportedly working on this, but who knows)rarely happens, but it bothers some people a ton so be aware
standard vs premium this is another thing just to be wary of as some go so far as to wish standard cars had not be in the game. In game while racing the standard cars look really nice(to me), but still photos especially close up they look awful
No cockpit view for standard cars, doesn't bother me, but some hate like the burning of a thousand suns. Bumper cam http://www.youtube.com/watch?v=2B2vrbZRaZ0
vs cockpit http://www.youtube.com/watch?v=0OUZeG2Szqk
Visual upgrades for most rides fairly limited
Lacking some nice newer rides. No Porsche they have RUF which are a professionally tuned version of them however.Overall
I have not played Forza, no Xbox 360, so I can't compare the two many on both sides of this argument will claim "clear victory". I think it depends on taste. I personally think it is the best racing game ever, even with the flaws. I prefer sim style racing (forza, rfactor, Gt) to arcade(need for speed, burnout, etc) so that will play a large part as well. I will buy any and all dlc they want to sell me and even though I am in crazy love and play this game every chance I get (many times when I should be studying or other chores) I can't wait for gt6.
Now if you are on the fence maybe wait for a good deal. Every gt cycle works like this first game on that playstation generation has plenty of issues, the next game in the gt series come out fixes most those issues are fixed and they add a ton of new cars. I am sure gt6 will be mostly premium cars, fix these issues, and add some other nice goodies.
Edit: hope this helps and is readable a bit sleepy