5. Jock Stein - well documented success at Celtic including 9IAR, 1967 quadruple (European Cup included) and numerous other trophies belie the mess he took over at Parkhead in 1965. His successful stint as Dunfermline manager shouldn't be underestimated.
4. Jim McLean - Scottish version of Brian Clough in bringing success to an unfashionable Club. 1 Championship, 2 LCs, as well as numerous finals and SFs including the UEFA Cup, and European Cup.
3. Brian Clough - brought massive success to both Derby County and Nottingham Forest. 2 back to back European Cups at Forest. Arguably cheated out of a UEFA Cup by Anderlecht in 1984.
2. Bob Paisley - took over Liverpool from the iconic Shankly and made them even better and more successful. Had an eye for a player as well as an able physio. 6 Championships and 3 European Cups in 9 years.
1. Sir Alex Ferguson - hugely successful in both pre & post Bosman eras where the balance of power switched from Clubs to players. His success at Aberdeen also prove he wasn't a "chequebook" manager.
Overall, a very subjective subject but for me SAF wins due to 1. His sustained success. 2. His success at both fashionable and unfashionable Clubs. But mainly 3. Success both pre and post Bosman era.
I wonder how the others would have coped with modern day player power. I'm not sure Clough or McLean would have adapted as well as Stein or Paisley tbh.