Get Guile or Evil Ryu
To be able to play as Guile or the evil Ryu you have to go on World Tour and build your character to level 30 and 31.
Super Akuma
also to fight Super Akuma in the Final Battle mode go to final Battle and pick a character and hold L1 and L2 before the VS appears.
Shin Akuma
You must first open up Final Battle Mode by beating the game on difficulty 7 or 8.Once you do this,Select Final Battle Mode from the Main Menu Screen.On the Character Select Screen,press and hold L1+L2 and choose your fighter.Keep holding it until the VS. Screen appears.You will then see Shin Akuma.Now your Final Battle fight will be with Shin Akuma instead of M.Bison.