Does Player A win or does the game continue?
In case of a tie, continue playing until a clear winner emerges.
There's clearly a tie in the number of Keepers, so you must continue playing.
Player A is not the player with the most Keepers. He's merely a player with the most Keepers. It is explicitly stated that the game does not end in the event of a tie.
It could have been written "If someone has 5 or more Keepers on the table, and if a player has more Keepers than any other players, that player wins."
To win, one must have 5 or more Keepers [satisfied], and one must be the player with the most Keepers [not satisfied].
Player B can't win because he has insufficient Keepers and because he has a Creeper.
Player A can't win because he has insufficient Keepers.
GendoIkari's answer is self-contradictory. "Until a clear winner emerges" only applies if the players keep playing, but he suggests that Player A should win rather than keep playing. That rules out letting Player A win. The only way around that self-contradiction is to keep playing until the tie is broken (or the goal changes, etc).