The characters:

Ryu and Ken are completely identical, but the CPU has a different fighting style. They are very strong.

Guile is very strong too. These 3 characters are the easiest to win with.

Chun-Li is the fastest, but she's weak.

Blanka is strong too, but he's a bit hard to control and he's too big, so he can be easily hit.

Honda is strong, but very big, and he jumps too small.

Zangief is the strongest, but he's very slow and he's too big. He can hardly jump.

Dhalsim has the most specialities, but he's extremely slow and weak.

Sorry, but my English is too poor to describe the specialities.