[Roll]

Game and Movie wise. Not storyline and official wise, akuma. Shin Akuma, like I said, is just the same as regular Akuma, only he doesn't hold anything back. Officially, he's not the strongest character either. Rather, Gill is. Ryu doesn't even come close to Akuma in power, and if he gave into the dark Hadou, then he would be a match.
But they both had to go into a lot of training to get to where they were/are now. Sakura literally started her street fighter career, about one year after she saw Ryu fight in the first SF tournament. In that time, she had her Ki manipulation abilities at the same level as Ken. Now, that was in one year of training. ONE year. Capcom does state, actually, that she is a fighting prodigy (and a school girl). Imagine another year after that. Now, when she gives into the Dark Hadou, and she will, what do you think will happen? I believe, that not only would she be stronger than Ryu, but she could become stronger than Akuma after a bit more training. That, Akuma, is why I think Sakura is the best of the street fighters in the list above. Because she's a good fighter all-around, and she's got the potential to be the best there is.
You just can't beat a girl who can stop a rampaging M. Bison with a giggle and a point.