I can't justifiably say that K' is the King of Fighters. Throw out nostalgia altogether, and K' still doesn't make my pick for the King of Fighters. He is one of my favorite characters to use, his moves are awesome, and he has a cool persona, but he's just not the best of the best. In fact, while Kafuin_gaira's post said nothing about Kyo or K', he did mention Terry Bogard. I'd even go as far to say that Terry Bogard would be my pick for the ultimate King of Fighters. I am a huge Kyo fan as well, and I think some of my angst for Terry as a whole comes from the fact that so many people I know and have come in contact with, exclusively use him and use him well. Although Kyo was originally slated to somewhat be the new SNK frontman, and almost overshadow Terry with the new series, I still feel as if Terry shines through. I understand that this isn't exactly what you were asking for, but I'm also going to say Terry Bogard, but if it comes down to Kyo and K', I say Kyo.