They aren't all like that, it's really car dependent, for example i've done off the top of my head 122MPH in a Ford Capri 2.8i, 140 in a Mondeo ST220 on GPS.
The Capri felt like I was going way faster than 140 did in the Mondeo, in fact it felt down right terrifying, I remember after I backed off that my hands ached as I was gripping the wheel so tight, even more surprising being that the Capri was on a private Motorway & the Mondeo on a private A road.
(The Capri incident was only because I lived 16 miles away from my now wife & she called me at 1am and promised nice things if I could get there before she fell asleep)
I've had goes in much more modern stuff & I just can't get my head around how you can have fun in them on a public road, for example i've hinted to the wife that i'd like to get a 5.0 Mustang, however realistically I don't see how I can have fun driving it on a public road without ending up putting lives at risk.