Daigo used Ryu in ST, but he started with Guile and Boxer as far as I know. Those are the 3 main characters he uses in SF2. He uses Sagat occasionally.
In Alpha 3 he used Akuma, but then switched to Ryu. In CvS he used Guile and Ryu. In Cvs2 he used Guile, and Sagat as the two main stays with like Cammy, Chun, etc... as his 3rd character. In Fighting Jam he used Guile and Urien. In 3S he used Ken. In SF4 he used Ryu, Guile, Evil Ryu, and Yun. He recently said he would really like to use Guile some more, but that he finds Guile lacking to win with him.
I've always thought of Daigo as Ryu and Guile, though most people just associate him with only Ryu.
This coming from a Daigod worshiper sons.
The only one you can be certain of is Mago. He is 100% a Karin fan. I feel like EG is just jumping on the bandwagon, but Mago's favorite character really is Karin and he told Capcom last year that he wanted her in the game. He already said he's going to main her even if she was low tier. Also, Snake said he was going to main Birdie unless Gief is in the game.