I think Irina and Michelle had the best rivalry why?
Because not only did each other's presence raise the other's performance level but they were both conducted themselves with highest degree of mutual respect. Needless to say I feel that the best rivalries are friendly ones.
Witt and Thomas was a great rivalry too but I always got the impression that they hated each other.
Lu Chen and Surya Bonaly had a rivalry of sorts...with lulu coming out on top most of the time.
Tara and Michelle had the best skated rivalry IMHO.
Hughes and Butryskaya often fought for 3rd after slute, and kwan.
Kwan an Cohen have a brewing rivalry....we'll see where this one goes!