Nothing on the ISI code (so GTL, GTR2, GTR2, F1C or rF) has very good force feedback. LFS is slightly better in terms of FF, but that's essentially an arcade game with some simulation features in it.
NR2003 (and the free GTP mod that can bolt onto it) is by far the most realistic. GPL has the 2nd best force feedback, but it's now 8 years old, and the graphics is showing it. Still, I don't look at the shiny bits anyway, it's all about the physics, and GPL still rocks in that area.
Looking forward to the controversial iRacing.com product though.
//edit: don't touch nK Pro with a barge-pole. There's been no support since the day after release, and there's unlikely to be either. It's essentially the same as the free nK from years before, but with better graphics. The graphics are awesome, but there's no offline racing, and the online is horribly broken. Still great if you like hotlapping, but it becomes rather boring rather quickly.