go here for the SF storyline

http://orochi.com/sffaq/characters.html

The Street Fighter storyline is kind of confusing because

1) They always update it with revisions (for example, Sagat wanted to kill Ryu in SF2. But, now, in the GBA version of SF2 they just released, he just wants a fair fight).
2) It's in Japanese, so stuff gets mistranslated or left out.
3) Come on, let's face it. It doesn't have much story period.