Sorry to say this, hope you are not mad, but it seems impossible that you are in a great relationship if you are so easily impressed by another guy. If a person is so in love they are close to marriage they understand that although other people can seem exciting (because they are new), it is the person you love that meets your essential needs. That is what is important. If you are going to get married it seems you should feel like he is special beyond anyone else. Ever look up love in the dictionary? It means, a deep and abiding interest. I don't think you have a great relationship. I don't think you are ready to marry him. I wonder too if you date this new guy after a year or whatever, you might get interested in someone else. Maybe it is the newness of the relationship that you are really falling for. It is very powerful.