On my main character I did a million side quests. Yes, she was the Dragonborn, but there's also this whole war going on, and the Greybeards are sending her up and back and over to get things, prove things, learn things, and she's still who she is somewhere inside.
She takes the responsibility seriously, but she also takes the civil war seriously (and her eventual responsibilities within the Imperial army). She takes her love-life seriously (after it sneaks up on her). She takes her family very seriously.
What made me knuckle down to finish the main quest was the desire not to participate in the Dragonborn DLC until I'd defeated Alduin. It didn't seem narratively right to face "That's not a Dragonborn; THIS is a Dragonborn!" until I'd ended the major threat to Tamriel.
I still haven't explored more than half the Dawnguard DLC, and I've only finished building one Hearthfire house.
I'm still discovering places I hadn't encountered before.
On my self-indulgent "I've been transported to Skyrim, oh no!" character, I'm doing everything I can to avoid the main quest because I was transported into an Imperial raid, nearly beheaded, nearly killed by a shouty dragon, hauled out of the flames by I don't even know who, because it was all chaos, asked to tell the lord of the land thar be dragons, asked to help kill a dragon cause, "Hey, you survived one of those, once!", and also discovered I can magic prett heavily.
It's a bit overwhelming and terrifying as is. To throw in "You're the savior of the world, and our only hope, and also you have to kill a mega dragon, thanks," was like "Nope! Nope. I can't get out of here, but I don't have to be your thing. Nope."
So I'm hiding in the College at Winterhold. It's going to be a LONG while before I hit the main quest again.