Only recently tried picking up the game again, but I've been playing Rose. She has some marvel-lite elements that I enjoy: U2 being ouro/SS-ish and being able to FADC her slow LP fireball and move around freely while it's on screen. Also, I like Jojo, so I'm partial to the Lisa Lisa homage! I'm awful at SF4 though, haha.
I'm not even going to pretend I know enough about SF4 to say what Blanka would need to be better. He got little things in ultra like being able to FADC ex-up ball for a safe reversal, but charge characters always feel like they're at a disadvantage in the SF4 engine. When they're under pressure they have a harder time than others because you can mash out a reversal even if you know the other guy is pressing buttons like a nut. It's much harder to take advantage of focus attacks. The match also becomes torturous if you don't have the life lead. You lose access to so many important tools the second you have to walk forward. Viscant has said that in SF4, the life lead is a weapon. When you play Blanka you will feel the truth of that statement.