Yea in a way Paarthurnax was your only true friend in the entire MQ. Everyone else kinda just bossed you around or were just using you for their own gains.
There's that moment when you first meet him when he says something like, "I know you didn't come all the way up here just to chat with an old dragon." I didn't really notice it the first time through, but now it makes me so sad. He's been living in seclusion up there for... what, centuries? Millennia? He's a pariah among his own kind, and even if he weren't there haven't been any around for him to interact with anyway. He's limited to contact with the Greybeards and while they certainly love and revere him, they are 100% human and don't share in his "dragonness."
How long do you think it's been since he was able to engage in "tinvaak" with anyone that even approached being something close to kin? I know dragons are probably solitary creatures by nature, but still. It just breaks my heart now to hear him say that. FINALLY someone whose soul is made of the same stuff as his shows up, and it's only cuz they want something. But he's still cool with it.
I would glady go back and engage in as much tinvaak as possible, and I frequently go back there anyway even if there's no additional conversation left to be had. He must get so lonely.