Sir Alex Ferguson - Greatest Ever?

Sir Alex Ferguson announced his retirement today. He will end his 27-year reign at Manchester United at the end of this season. He will go out on top of England as the greatest manager in English football history. HIs resume:
38 trophies
13 England titles
2 Champions League Titles
5 FA Cups
1 Intercontinental Cup
1 Super Club Cup
1 Club World Cup

Too many others to list. Is he the greatest manager of all time? Who else makes the list?