Adam West - I loved the joyful campiness of the show, it hit all the cartoon notes and had delicious takes on the rogues gallery in a light, fun sauce
Obviously, this is the correct answer, but my heart is split between my love for Adam West's sublime brilliance and Will Arnett's masterstroke Lego Batman.
Here's another thing, for me: if the history of Batman movies has proven anything, it's that anyone can play Batman. The trick is making Bruce Wayne interesting. Michael Keaton played the most interesting Bruce as far as I'm concerned, so now I'm in a 3-way tie.
So, to avoid what to me seemed like the most obvious choice(s), I went with Clooney.
"CLOONEY?!?1?" you rightly respond.
Yes, I've decided to come out of the closet with my appreciation for Clooney's Bruce Wayne. Is he especially interesting? No, but Clooney's looks, charm, and charisma really sells a James Bond-like, sophisticated, handsome, '70s love-god, millionaire playboy Bruce Wayne. Also, he has the chin for it.