Ben Affleck just looks like he is bored and tired.
I feel his acting was very stale, if that's the right word? His Daredevil portrayal to me was better than him as Batman but he was also younger and had more energy. I understand Batman's attitude is a bit like he's just so done with the world, but Christian Bale gave Batman more depth and expressions.
I compare Ben's acting to Johnny Depp's acting in the newest Pirates of the Caribbean. Very much like some teachers who have worked several years and come to work often grumpy and negative. Maybe the personal issues affected both of them. We know they've both dealt with things in their personal lives, relationship-wise.