That's maybe making it too simple and using too many opinions.
No... and yes. It's my opinion. From all 3 games, the one I didn't try is FM3. That's why the items I picked from it are visual only, or visually-based like aesthetical damage and roll-over.
You can say that FM3 damage and roll-over isn't (visually) very realistic. I'll give you that and possibily you have tried out the game, something which, I remind, I haven't, so you'll probably right... but I mentioned because GT5

has no damage at all and - forgive me - until I see it properly I don't know if GT5 will have, or how realistic is it. For what I've saw at the moment from TGS videos it's... rubbish. (Ferrari heading to the rails and getting nothin but some paint scratches). So, lacking a GT5

/GT5 proper comparison, I'll go for FM3 damage.
As for scenery and track detail this is subjective. To me, background details are better on FM3 and track detail (tarmac, cracks, wear, dirt, etc.) are more real-life like too.
As for car handling, GT5

is very good, BUT fails in my opinion on the feedback it gives to you from the car/tire rolling on the track. My opinion - again! - Shift does this better, although on other handling aspects GT5

is better. GT5

(car handling speaking) looks more real, behaves/act more real BUT shifts feels more real, if you like. As for sound, Shift's definitevily better.
As for the rest, GT5

is way ahead competition I think.