Um, no.
There are a lot of little things that GT5 simulates very well compared to Forza, things that are apparent when you drive with absolutely no driving aids.
Drive the Zonda R in both games with no assists. In Forza, if you give it a little too much throttle in the turns, the tail starts to slip but you can recover it with so much ease & straighten out in just 2 seconds. Do the same in GT, and you'll more than likely have to be precise in your movements because trying to recover the tail can force it to just go the opposite way. This is due to the throttle sensitivity in that car being much higher than Forza's, and as I would expect, a lot more realistic for a 740Hp, MR race car.
Similar note, lift off oversteer in Forza also seems near non-existent because again, you can recover the cars rather easy through turns. I could start putting in decent laps with the NSX-R without ever worrying about having let off the gas mid-turn b/c then you can just tap the brake & power slide through it with a little throttle input.
In short, driving a lot of the cars, esp. the race cars, in GT5 require similar techniques that you have to use in GTR2 to set good laps, something I can't say the same for Forza because all you have to do is watch throttle input.