I have no opinion on Messi being the best player ever or not. My observation actually stemmed from a lengthy and well informed post made on the Barcelona forum around a year ago (after Chelsea had muted Messi in the Nou Camp game I believe) by a Barcelona fan who had doubts over Messi's "best player ever" tag. One of the games he used in his argument was Ronaldinho vs Milan in Milan, and, if I recall, his argument was that when his space was shut down by the best teams, Ronaldinho could still unlock a match, but that Messi finds it harder to do so. Tonight - the first match since the Chelsea game which spawned that post - Messi found himself in those circumstances again, and he was largely anonymous.
It's one game, yes, and I don't care to whom people attach the greatest ever label really, but I do find the discussion itself interesting. If you're trying separate the game's greatest players, then you can but only split hairs?