IMO, it's both physical attraction and hard work. I think that's what makes the "ideal" marriage. I also think it helps if you don't get married until you know who you are as a person and what you want out of life. That way, you are far less likely to fall for the wrong person in the first place.
I think the way "romantic" love lasts is if it's built on a solid foundation of friendship and values/lifestyles/interests in common. But, if my grandparents are any indication, it does exist. If I've learned anything from my life it's that opposites may attract, but they probably shouldn't get married. Different personalities are one thing--different life goals and desires are another story. When you have two people on two different planets, they are never going to get along no matter how much attraction they have for each other. But then again, if you have no attraction whatsoever, I sometimes wonder why you aren't just better off as friends.
My grandparents are going on 55 years, and some of them have been hard, but she still thinks he's really handsome and calls him "sweetie". He thinks she's the best thing he's ever known in his life. He has Parkinsons and can barely get around, but they love spending time together, and they love each other madly (seriously, madly--it's sort of gross!). They even hold hands in church! So, do I believe this sort of love exists? Absolutely. Do I think it's exactly like the movies? Absolutely not.
