No, he isn't at the moment. Reason being he's had a few form issues at the start of the season, and I still believe him to be playing in his second best position. But yes, I believe out of all the defenders we have, he is the one we can count on the most, and the one that is world class.
Whenever players go through a spell of poor form (for the high standards they've already set, particularly true with this player), there always appears to be one or two people waiting to kick them while they're down despite them proving to be top players against some of the best forwards in the world. It already happened with Buffon when people were wanting Storari instead, yet you have to go back to the cliché of "form is temporary, class is permanent" . Luckily someone took the time to dedicate a signature to the players which Chiellini has dominated in his career, otherwise there wouldn't have been as much accessible proof of it.
Last season was probably his most inconsistent, but in all other seasons he was undoubtedly great at the very least. The biggest concern of mine is how easily people forget the form Chiellini showed during the 09/10 season, when he was almost literally carrying the entire defense along with him. That was probably the one season that I thought he was arguably the best CB in the world (instead of being top 5), purely because of the way he was keeping Juventus alive in games. The experienced Cannavaro was often a passenger in the defense, while Giorgio had to compete with everything thrown at Juve. I clearly remember the Napoli game which we lost 3-1 at the San Paolo, when Chiellini was the only outfield player that delivered anything useful (close to being a flawless display from him) in a completely humiliating game. That sort of performance defined him, yet the form he showed at the time is often lost amongst the disaster that Juventus was and people group him in with the Diego/Felipe Melo/Grygera type players because of the collective form of that Juventus team.
Judging from posts all over the forum, some seem to think he's a mindless baboon that lunges into tackles recklessly because he doesn't know better, but he's often the defender that stays goal side of the attacker and doesn't step in needlessly (hey Bonucci). They also believe him to be mentally retarded with the ball at his feet because he cannot pick out a pass like Mexes or someone like that when he'd be perfectly fine at doing a similar job to Barzagli of playing the ball short to a midfielder or a fullback. If anything the left back role highlights his ineffectiveness in possession (despite that one very good assist he had this season).
As if any of this needed to be said anyway, shame that some have the memory of a sieve.