Thats a tough one Jules, and Im not sure actually.
I always liked Brian Clough as a neutral in my early years of being a footy fan, because he knew how to get the best out of each individual, whether they were that good or not etc.
I seriously think Alex Ferguson is over rated and I refuse to call him 'Sir' by the way. And this is because I dont think he and Wenger and Mourinho and Guardiola etc, would be able to bring a team up from the Conference without the money and the star players that they are used to working with.