I admit, I haven't seen Argo and I wondered about that performance. And what I'm thinking/asking has nothing to do with his real life intelligence. Some people sound intelligent but really aren't. Others, vice versa but with movies and acting, I'm not sure scripting intelligence is enough if the actor can't pull it off. I mean, I felt in Daredevil, Affleck made for a good attorney at least conceptually. They didn't really get into how good of an attorney or anything but the looks and sounds of the guy was believable enough to me. But to me, Batman has always been high level intelligence, not just a guy that graduated with a law or medical degree. Someone who got perfect scores on SAT's but is still grounded with common sense intelligence. And a psychological understand beyond that of casual knowledge.
Bale, to me seemed to fit this mold. To me he seemed like he would have been the kind of "brat" that got A's in school without ever studying. One of those guys that just has a knack for things and they always work out in his favor. And that deep psychological understanding as well. Affleck is more like a guy that did better than average in school and might do one thing very well but that one thing isn't necessarily anything physical. If they remade A Few Good Men and cast Affleck, yeah...I could see that complete with the hitting softballs scene. But Batman (and let's just use Nolan's version as the barometer), not so much. It's closer to George Clooney playing the character. That's just my opinion though.
Oh..and Matt Damon as Jason Bourne....that totally fits IMO. That character is more about being programmed and trained as an assassin. Not an operative who is capable of doing those things naturally and instictively.