Just had to reply to this - I was exactly the same! It was really just a sad feeling when I got control of Desmond first, then when I first saw the hallucination of Ezio helping Desmond my eyes watered.

The final straw, though, was when Desmond commented on how old Ezio looked that last time he returned.

Spoiler! - Will also admit to whining like a puppy when Ezio walked out of the Colosseo at the end.

Want OP to know I'm thinking about this, but won't tag it just yet - I made that mistake with two other posts I've yet to fill.