I dont understand why everyone says Ferguson like it's not even a debate. Ferguson had a lot of advantages in his first 4-5 seasons that ETH does not have. And no I am not saying ETH has a harder job, just that it's not quite as obvious as some seems to think.
Managers weren't fired as quickly as they were today - Ferguson would never have survived the 89/90 season in todays climate. After outspending everyone else, we were as bad as Chelsea were this season. And if fans had their way. Ferguson would have been fired, he was really unpopular. If ETH ends 6th or 7th next season - he is gone.
Yes Ferguson took over a weaker side - but after a couple of seasons he was also able to spend money like no other club in England could - in the summer of 89, United spent a lot more than everybody else - Arsenal who won the league before spent £500.000 on Siggi Jonsson, Liverpool ended second and spent £800.000 on Glenn Hysen and Steve Harkness. We spent about £7 million on Ince, Pallister, Phelan, Webb and Wallace. Today, there are 5-6 clubs who will spend as much as we do (or more) - and spend the same amount on wages as we do. So let's not pretend Ferguson did not have a huge financial advantage for a lot of seasosn.
In addition - Liverpool and Arsenal were already passed it by 1990 - once Ferguson survived that season, the competition were a lot weaker than 2-3 seasons earlier. Especially Liverpool had a lot of players in the late 20s like Barnes, Whelan, Houghton, Nicol, Beardsley, Rush, Hysen, McMahon etc. And let's be honest here, the Arsenal and Liverpool-team around 1989/90 were not topclass in Europe - City and Arsenal today are. So Ferguson didnt have to create the best team in Europe, just the best team in England. ETH needs to get the best team in the world to win the league.