The physics started being too dumb and floaty when they moved to PS3 with THP8. They were pretty consistent from THPS until THAW. The best looking ones, in terms of fluidity of animation, are 3 and 4 (but especially 3). I don't know, I just feel that the PS2 series are the best skateboarding games that will ever been made. They're all I play (except THPS2 for GBA).
I haven't tried SKATE much, but it also looks dumb and floaty. I just cannot get past the broken bones thing, it's even more disturbing to me than action figures