Don't want to be rude, but saying "Ryu is more iconic than Megaman just because Ryu is more popular" is like saying "Frogs are cold-blooded, therefore frogs are reptiles." which isn't true.
Take a look at this fanart.
From left to right, Megaman, Bomberman, Mario, Sonic, Crash Bandicoot, Rayman, Pacman, and Banjo.
If you replaced Megaman with Ryu in this artwork, Ryu would look blatantly out of place. Megaman is a cuddly character who can fit when he is grouped with Mario, Sonic, and Pacman.
To get back on topic, I would certainly prefer another Sonic character over Chun-Li.