Going on a cruise to get married/honeymoon. What is the best line and ship?

Getting married/honeymoon on a cruise. What cruise line and ship are the most romantic/elegant? Not to crowded? We are in our late 20's. When I was a teenager I went on Royal Caribbeans Sovereign of the Sea. Was AWESOME!! Now im looking to take my future husband on his first real vacation. Suggestions would be great!!