The game is only 3 weeks old, there is no tier list and no matchup list yet. Even CGoH (the Japanese release) was not out long enough for a tier/matchup list to be agreed upon even by the people who followed it closely. Karas, Chun, and Ryu were universally considered high/top tier in CGoH though, but Karas ate a 600 pound nerf bat to the face in UAS, Chun and Ryu remained mostly the same except infinites were removed and other characters were made better. In the little discussion that has occurred so far the most common contenders for speculative top tier spots are Zero, Chun, Jun, Yatterman-1, Ippatsuman, Polymar, Karas (he still has great pokes and mobility, just no more infinites that can start from any move) and Tekkaman Blade. It's really up in the air but what everyone does agree on is that everyone is viable (as long as you stay away from G. Lightan).