You have to be attracted, but they do not have to be a 10 or even a 9. You have to want to have sex with them, that's about it.
Most of the guys I know (all actually) who say "my girl has to be hot, I can't help it" are generally the guys with bad marriages or chronic bad dating experiences.
Having been with my wife for over 9 years I can tell you looks don't even make the top five "what's important in marriage" list. This does not mean my wife is not attractive, she is. That being said, I see probably 40 "hotter" woman every day, she the same with men. We both know it, neither of us care. We are without question the happiest married/dating couple I have ever known.
Trust me, you 10 chasers have a VERY slim chance of living the dream, for reasons which are terribly obvious, proceed at your own peril
Side note: I've always found the best woman are the "something about her girls" for whatever reason. These are the woman you know are not 9-10's, but for some reason you can't take your eyes off em. Maybe it's the eyes or the smile or whatever, these are the good ones.
Edit: LOL, I'm bad. I've actually been with my wife for 14 years. Wasn't thinking.