I just find it really impressive that after 1000 years they are still together.
They went through a lot of crap, hurt each other a lot and still are together.
Relationship between other Mikaelson siblings are all ruined: Finn tried to kill everyone, no one gave a damn he spent 900 years in a coffin. Kol tried to kill Bekah, even Elijah didn't care he got killed, Bekah got over his death in 5 minutes. Bekah said that Klaus hated Kol.
Rebekah spent a lot of time in a coffin and yet Elijah didn't care enough to put his foot down and demand Klaus release her.
Elijah is the only one who didn't get daggered throughout 1000 years. He is too precious for Klaus to spend even a week without him
Elijah got over everything Klaus' mood swings threw at him: Tatia, Celeste, Katherine, god knows what else happened.
No, for me The originals will always be about one relationship Klaus/Elijah