Both those teams had to sell their best players though and were both struggling financially after the Serie A bubble began to burst, won the Coppa Italia with a withering Fiorentina in the first season as a manager is a decent achievement tbh. He did well at Lazio too.
His sucess at Inter is akin to O'Neills at Celtic, dominated in leagues which were on the slow decline with no real competition and don't really say a lot about ones managerial abilities.
He's a good manager but not done enough to be proven one of the best, it's only fair to judge him once he's had a full season and his own team under his belt IMO.