Not overly-fussed about his choice of clubs, though it'd certainly be interesting to see him try and do something with AC Milan for example, but I don't think he is the very best around. He is great, just not the best.
He built a sensational Barcelona team, but one that was absolutely annihilated by Heynckes' Bayern (albeit under Tito). Then at Bayern, he was soundly beaten by a direct Real Madrid outfit. Maybe you could argue he hadn't put his stamp on the team by that point, but then Barca took them apart the following year too. Expect them to do the same again if they meet.