You might be the only other person I know other than me that has both of these in their top 3.
I think Mothra vs. Godzilla is one of the best Godzilla movies of all time. I'm not a film critic, so I couldn't break down every aspect of why it is a great movie, but it has all the elements I love; a great story with purpose, a colorful and creative presentation, seriousness and humor. However i didn't put it there solely based on its quality, but its entertainment value for me. It just deserves to be in the top five any way you look at it. And thanks, by the way. I like to think I have a decent taste in movies.