I’ve won with plenty of characters. Sagat, who plays a lot like them. Guile, Fei Long, Chun Li, Vega. I’ve beaten the game with just about everyone, except Dhalsim. This includes the original Street Fighter 2s plus the Alpha series.
And no, the dragon punch and fireball are not “impossible” to defend against. Every single move in this game is blockible except the grabs. There are methods to counter everything. I give it to you though, the fireballs are annoying when spammed, and the dragon punches make it very dangerous when jumping towards the guys who use them. Sagat with his tiger projectiles and upercut is actually the worse though. Fortunately, he seems weak at the knees, I usually win by tripping him every time he tries to huck balls at me. Of course, you have to get in close to him first.