I finished the last dungeon, collected all the extra stuff and every side quest I could find. I literally got right up to the lead up to the final Gannon fight... Then I was like "meh, I'm done".
i do this all the time. when i get close to finishing the game, i HAVE to go do all the side quests i neglected to finish along the way. Then i get burned out and beforei do the final boss... But my SO has similar video game tastes as me, so i end up just watching him do the final boss on his save hahaha