(SPOILER): I can see that Dan really loves Blair more than Serena.
Dan's feelings for Blair were so much deeper than his feelings for Serena. It's weird, even Penn dated Blake for three years though. The chemistry between these two was amazing and they were so much better for each other, to be honest. Too bad the writers fucked over their relationship. Dan saying to Serena that she's always been "the one" will always be a huge WTF moment of GG.
So, I just pretend this scene as the final one and the rest doesn't exist: https://www.youtube.com/watch?v=-j1R_RA5hac