But he was very good at one point of time and given the set of players he put together, as good if not better. He has proven to be far inferior over a period though even considering circumstances.
History has had massive companies that are so far ahead at one time but fall behind as they fail to innovate with time, exist in denial and grind into being nothing.
Also, Fergie knew when his time was up. Wenger doesn't seem to understand like a lot of people who don't know when to exit.