Weddings, as a whole, I think are supposed to be sappy. The problem is that real life weddings, again, as a whole (I'm not talking about the couple who gets married in jeans in their backyard or other such weddings, I'm talking about Church/Temple/designated wedding venue weddings) weddings are not the most exciting events. As a guy, I can't remember a wedding I went to where I wasn't a little bored, at least. So I can forgive movies and TV shows with going sappy and cliched.
What I don't like are movies predicated on a man or woman (though usually it's the woman) engaged to someone else when the movie begins, who finds her true love, dumps the other person, and marries the person they meet. I'm not advocating staying with someone you love, but the cliched "the person I've been engaged to is boring, this new person I've known for less than a week is exciting, I'll marry him/her" needs to be retired.