It's unclear whether this is a statement as per the thread title or a poll as per the fact that having made a statement you've then asked people to vote. If it's a statement then I'd have to disagree as a captain shouldn't heap so much shame on his club on numerous occasions or sleep with his team mate's girlfriend. Also Chelsea should have won more league titles under his captaincy. If it's a poll then I'd go with Keane as he was the on field driving force behind United dominating the PL for a sustained period during his time as captain. United won 4 league titles in 5 seasons under Keane's captaincy. Chelsea have won 3 league titles (soon to be 4) in 13 years under Terry's captaincy. Not an impressive record given the financial muscle Chelsea have had for 10 of those years. Some of the lack of success must be put down to the fact that the captain was complicit in undermining several managers. When the captain thinks he's bigger than the club/manager he's failed as a captain. Keane reached that point with United and was dealt with. Chelsea would probably have had more success had Terry not been involved in destabilising the club in between Mourinho's tenures.
You have to look beyond the basic facts as the trophy haul could be down to an overall team effort, a captain is someone who drives the team on, who wins a tackle at a vital moment or scores a goal. Terry certainly fits into the category as he's done a lot ensure Chelsea have stayed at the top but "the greatest"? not so sure about that.
The BBC did the same poll on Saturday on their live feed, though with more choices I think. From memory I think Keane won and Terry was 4th or 5th behind Gerrard and Adams too, though I might be wrong. For me John Terry is a poor captain who has caused division in his teams and seems far more concerned with promoting John Terry rather than his teams. I hate Roy Keane with a passion and think he is a horrible individual, but as a captain he is so far beyond Terry that they aren't even on the same page as far as I'm concerned. Best contrast - look at how each of them approached celebrating a European final they were banned from.
Terry really shouldnt be considered here. For team hes been in and the fact hes been carried his entire career by actual defenders like has masked over what is in effect a rubbish footballer and a worse man.
Seeing as all Liverpool fans would go for Gerrard, Utd fans Keane, Arsenal Viera etc what would be rival fans reasons for it not being Gerrard?