I have a tendency to come into popular TV series late. Buffy the Vampire Slayer? I started watching in season 6. Smallville? Uh...on DVD right around the time it ended its run. (Yay for jumping on Supernatural from the start! But...it doesn't take place in high school, so we'll save that for another day's analysis.) But one great thing about watching so much of these shows all at once is that the trends kind of whack you over the head with a two-by-four.
Buffy and Angel I understood. He was instrumental to helping her save the world (or occasionally trying to destroy it himself) more than once. So that was a romance that fit right in with her being the chosen one. But her other romances? Not quite as much.
And don't even get me started on Clark Kent. Seriously, boyo, save the world or get the girl.
There's a delicate balancing act when you're dealing with world-ending matter and dating. How many times did Clark have to ditch Lana to go be a hero before she got the message that he had something more important going on? (Granted, he did, but since she didn't know, that isn't the point.) And Buffy? The only boyfriends that stuck for that girl were the ones who also weren't quite "normal", and every one of them that lasted knew she was the Slayer. And you know that the love interest always ends up in trouble, especially if they aren't super-(or supernatural)-powered.
So how does a character decide what matters most? The love-interest or "the world"? One's immediate and one's...kind of vague. The balance of one life you know and care intensely about weighed against the many strangers. And what does that decision say about them as a "person"? The copout, of course, is that they can manage to save everyone. Sometimes it works. Sometimes though, it just looks like a cheat.
As a writer, it's something I try to weigh very carefully, because reality says it can't work every time. At some point, the character has to decide and someone has to lose.