Ima be as straight forward as i can about my expierience
I purchased Forza 2 waiting for the next GT5.
I was suddenly very spoiled by the damage and the livery editor.
Suddenly Forza 3 came out, and thanks to all the fun times with 2, i said "Why not" and spent just as much time in it. I found myself stressed just a bit by the wonky menus and it's fetish with saving between every screen, but the community was fun, the AI was a decent challenge, and i spent way too much time in the livery editor. xD Not to mention, it was my first chance to really get a feel for my Fanatec PWTS, and i thought the driving was perfection at times with that wheel.
GT5 was delayed a year, i was hoping it was to take all the great ideas being tossed out in racing genre and reconsider some options.
Dirt 2 Came out, it was my first time really getting a handle of some amazing Direct X 11 capable racing, i was officially spoiled by the interiors, the damage, and the wonderful windshield effects with wipers, water and dirt. Not to mention, i was amazed with how well the game handled the Fanatec, even on PC. It was about the time i learned the hard way not to strap that wheel to unstable surfaces, much less foldable tv trays, it nearly threw it aside. xD
Finally GT5 came out, of course i picked it up asap. The list of things i was put off about was staggering, things such as loading screens between every menu screen, awful UI design, previous gen style AI, awful rain on windshield effects, i found the more i played the longer the list got, even if i tried to stick to just premium cars, which effectively got me to thinking that Forza3 really had a bigger car list..
In the end, i'm sitting here playing Gran Turismo 5, not Forza 3. I think the reason is obvious, while Forza my be consitently prettier, or feature damage, or handle my fanatec better, i find that GT features the most realistic driving physics i've ever played with. I find myself learning something new all the time with the liscense tests and special events, and i'm loving the lounge-like casual online play. Not only that, i feel that the tracks are much more similar to their real life counter parts, and on the side, the interiors to the premium cars are often quite prettier anyways. xD
When i wanna play a more complete "Game" i may be heading back to forza eventually, however i find the physics in GT5 holding the game up alone, and despite all it's shortcomings, i don't have a problem with that.