I like the roster and concept of 2003, but it's kind of a mess in competitive play. I did have fun with it though. XI improved on it in just about every way (except for XI's lack of Billy and Yamazaki).
My big problem with the game is that it "feels" off. I'm not sure how to describe it, but the hits don't feel solid. I don't know if it's because of the graphics, or sound, or something else, but punching someone in 2003 doesn't feel very satisfying. For a fighter, that's a big problem for me.
My other minor critique is that the LDM system doesn't feel very developed. Some characters (Kyo and Iori) get LDMs that seemed reminiscent of their 2002 HSDMs. They look very impressive and cool. Other characters (Leona and Clark) just get SDMs. It feels incomplete. (Of course, this is also true for XI, but less common.)