Since I like Christian romance, I thought I'd add my two-cents worth on some cliches I've noticed:
Girl is pure and perfect (as mentioned), guy has a rough background and feels undeserving of girl.
Now, I'm totally not against purity. In fact, I'm a huge advocate for it. But I think many times in romances, the poor guys get picked on too much. Why can't the guy be the pure one for a change?
As far as all the characters being good-looking and whether or not someone would read about "ugly" characters, that's a hard call. I kind of like it when the character thinks they're plain and unappealing, while their eventual mate thinks they're beautiful. (Or handsome -- it goes for the girls and the guys.
) That may be cliche too, but it seems realistic to me.
It might be neat to have a story where one of the characters is handicaped or something -- just to show that true love is not dependent on perfect looks or abilities. . . which no one has really.