Grid's pretty decent. You can download a demo version. It's pretty much an evolution of Pro Race Driver/TOCA. I haven't played the games you listed so I can't compare.
Personally, I thought it was relatively easy. I was able to win at Jarama (a track I've never even played) the first time I played it. Oh, and I probably had four or five drinks before playing. I kind of like it better than GT5 just because of the damage and the fact that you can spin other drivers out and that they can spin you out too. In GT5, they can spin you out, but you can't get them back, which I think is BS.