This depends on so many variables. First, how committed to your individual religions/churches are you? Will you be willing to attend church at either a catholic church or the church of choice (Methodist, Baptist, Lutheran, etc.) of the Christian? What will you do when children arrive on the scene? How will you rear them? What beliefs will you impart to them? What are your discipline theories with regard to your respective religions?
I believe that you can make this relationship work if you are 100% committed to one another. Let's be honest, both of you are Christian, you just attend different churches...the age-old Catholic/Protestant debate which Elizabeth I and other monarchs of England, Spain, etc. have known so well. It will be ten times better in your relationship than if one of you were a non-believer.
My advice? Go to pre-marriage counseling with a non-partisan counselor. Think aloud through all the things that most people don't before marriage: children, discipline, how important religion is to each of you, parental pressure for conversion, money, squeezing the toothpaste in the middle, etc.
Best of luck to you!