Alessandro Nesta, how good was he?

The best CB i had the pleasure to watch, by a huge margin. Stam would be the 2nd best, and then the rest
 
Seen Terry's name mentioned in here a few times and found this funny take from 2010. Also slaughters Carragher.
https://thisisfutbol.com/2010/11/blogs/world-footballs-overrated-xi-i’m-just-not-that-into-you/

Centre Back: John Terry (c) (Chelsea and England): Overlooking his leanings towards the ‘crap human being’ end of the spectrum, Terry is and has always been overrated. His chest thumping style was always going to earn him plaudits in England, a footballing nation that values perspiration over inspiration. When Jose Mourinho was in charge at Chelsea and they were winning the Premier League at a canter, posting record shattering defensive statistics along the way, it was Terry that was largely credited for that parsimony.
But for me, there are a couple of key caveats: 1) Ricardo Carvalho, who at his best, carried Terry by bailing the former England skipper out with his exceptional pace and reading of the game. As an aside, how much could Chelsea do with the Portuguese now? 2) Chelsea’s generally defensive outlook with Claude Makelele patrolling the area around the back four, meant that their team was compact and exceptionally difficult to break down. Essentially, Terry enjoyed safety in numbers.
Compare this to Nemanja Vidic and Rio Ferdinand at Man United, who excelled for a sustained period between 2006 and 2009 despite never being afforded the protection of a destroying midfield player and being part of a cavalier side that habitually left the back four exposed thanks to their attacking travails. Now that Chelsea have regressed somewhat, Terry has been exposed for what he is: a limited, last-ditch merchant with the turning effect of an oil tanker being driven by Rik Waller. That said, he’s better than Paulo Ferreira.

Nah, i don't agree.
He did look shaky for a while after 2010 (with Scolari and AvB), but with Ancelotti, Hiddink and Jose, he was a regular starter and reliable defender in league-winning sides for 5 years more - by which time both Vidic and Rio had very badly dropped their level and retired. Terry made partnerships with luiz and cahill, long after Carvalho and Makelele were gone. Ancelotti's team wasn't particularly defensive and he did fine.

I don't think he needed Carvalho or a super-defensive setup with dedicated DM, but his one consistent weakness was defending in a high line. There was a 5-3 loss to Arsenal where RvP and Walcott tore through them, possibly worse than Vidic in the 1-4 vs Torres.
 
I'd say Nesta is the best I've seen in my lifetime. Cannavaro is rated so highly because of the 2006 World Cup because he was an absolute machine and probably had the best individual performances from a defender I've seen.

Rio is definitely up there too, he was top class and similar to Nesta in many aspects. Them two are ahead of Cannavaro IMO who's in there with Samuel, Vidic, Lucio, Terry, Puyol, Stam etc.