I main Raiden, and in a way I kind of see myself as the player most representing him. I've mained him in every MK game he was in. I like to think of myself as the best player for my character, but the fact of the matter is not too many people represent him at a high level. The most known Raiden players besides myself are JOP and Justin Wong, and I've been told by several people that neither one of theirs is anything like mine. These happen to be the only two Raiden players I was somewhat impressed with (JOP at PDP, not EVO, and JWong at Sin City Heat).
JWong is just an overall great fighting game player with great fundamentals, but he doesn't really invest much time into MK or know the character as thouroughly.
I've played against and beat many top, known tournament players offline (not going to mention any names), and most of them (win or lose) say I'm the best Raiden they have seen or played against by far. I didn't go around claiming I was the best Raiden, I've basically just played against great players and that's what they all say.
Sure I feel a little cocky about it sometimes (moreso confident), but that's only because I have so much experience.
I'm sure there are other Raidens similar to me who simply haven't surfaced, and I know anyone who is fundamentally good at this game could pick the character up and learn to play him in a similar manner. Only some things come with experience, though.
Besides Raiden I at least have the basics down for most of the roster, save for a few characters.
I loled @ UK players being better than US players with their respective characters. Naturally I understand you'd like to think so, but that's essentially not true.
The only impressive thing I seen from Nivek is aa jump punch into B312 superman, unfortunately. Dont get me wrong his Raiden is good, but from what I seen he played sub optimally, and inconsistently.