Here's my opinion.
There have been some great and not so great performances by various
actors as Batman, but the success/failure of the various films has
to rest with the writers and director.
More than any actor being the "definitive " Batman, I think it's more like
was that actor portraying Batman correctly within the film they were
given.
The question isn't so much "Will Affleck's Batman equal Bale's?" because
really that's what we're all thinking. Bale set a new high as Bats.
Instead, the question is " Will Affleck's Batman be convincing and enjoyable?"
this is a different Batman, a different universe (I think, I'll have to ask
Nolan next time I see him, LOL !), we have to see how Affleck performs
given the script that he's given and Snyder's direction.
All in all I have very high hopes, I really enjoyed "The Town" . The biggest
challenge will be the voice (and hey people, Bale has done some stinky
films too !).
Here's my personal Batman rankings.
#1 Christian Bale. While Batman is about fear, and conquering it, Batman is also about anger, about rage, and nobody does rage like Bale (e.g. the Joker' interrogation room scene) . I liked the Nolan films, and I think Bale did a great job in BB, establishing the character from scratch. Nolan provided the script,the direction and the aesthetic. Bale made excellent use of it, he's a great actor. (Any Bale fans who haven't seen the Fighter, there's the proof).
I grew up with Dark Knight Returns and Batman Year ONe, and I felt Nolan was the closest to capturing the spirit of that material.
#2 Michael Keaton. Trod a fine line between serious and silly, but did it brilliantly. Burton's Batman was very much an 80's creature. It worked back then, and is still an enjoyable watch now. You like Keaton's Batman, but
he's not as intimidating as Bale's Batman.
#3 Adam West. I remember being a kid in kindergarden and coming home to reruns of Batman. Pow ! Bam ! It was incredibly silly, but it got the caped crusader through the 60's, and the great Batman stories of the 80's/90's (and those more recent, like the Court of Owls) are a reaction against it.
I reckon whenever a Batman writer writes a funny line in a comic, an editor makes him watch Adam West do the Batusi, and have a re-think1
#4 Val Kilmer. Did the best with what he had, but didn't bring the presence that he brought to his more iconic roles (my favourite being Doc Holliday in Tombstone), he owned those characters, but it felt like he was only renting the Batsuit. A lot of that blame has to fall on Schumacher, but Kilmer is good enough to do better with that material ( case in point, Jim Carrey stole EVERY scene he was in, and his lines were even more ludicrous, Tommy Lee Jones was simply dreadful).
#5 George Clooney. Do I really have to explain this ? It's true, he had crap material to work with, but really good actors can do amazing things with small roles. Clooney phoned this one in.
How will Affleck fare ? If he can play off Cavill, Adams and Cranston well,
and make a passable attempt at the Bat-voice, then he should be fine.
I think he's a much more legitimate choice than a lot of the other guys considered for the role (although Gerard Butler was my favourite).
As I said, I have high hopes for Affleck, roll on BM vs SM.
Peace.