It's informal, it's anecdotal, but the people I know who like Keaton's Bruce/Batman either were very young when they saw 'Batman' (therefore, he was their first exposure to the character), or they had no real knowledge of or investment in Batman comics.
At my comic shop, no one was happy when he was cast, and no one- NO ONE- had their opinion changed after the movie came out.
The agony was compounded a year later when I saw Alec Baldwin in 'The Hunt For Red October', an actor who could play the intelligence, intensity, physicality- and he looked like Bruce Wayne brought to life. And he had the voice without having to force it. And I realized that he'd been in 'Beetlejuice', the film Burton had shot just before 'Batman'. Unbelievable.