The Keaton casting worked very well, certainly better than the more conventional casting of the two guys who followed him. The evidence is the tremendous success of Burton's Batman films, which radically changed the approach the studios take to this day to superhero fare and paved the road for currently popular stuff as diverse as the recent Nolan trilogy and the X-Men movies.
Movie audiences believed Keaton as Batman just fine. Some devoted Batman fans may not have; meh.
The battle in Nemesis isn't as good as the one in TWOK, not because of tactics or nebulas, but because one is the action culmination of the plot and the other is just there to be there.