It's hard to call someone who only won 1 Scudetto one of the best Italian players of all time or of Serie A.
That's because Roma was a smaller stage than one of the top Italian or European clubs, and it's always easier to shine there than have to play among players equal to your caliber or potentially better.
I respect his skills and his talent, i just think with the career he has had, it's difficult to put him on the same level as Buffon, Pirlo, Nesta, etc.
Having said that, i think he had what it took to be a star at a big club, and had he left i think he would've won at least a ballon d'or once. Lord knows how many Scudetti if he went to one of the big 3, and at least 1 CL if not more.
But i guess we'll never know, he sort of took the easy path by staying in Roma and we'll never really know if he had the capacity to be a real star.