I just wanted to relax on a beach for my honeymoon. Travelling was the last thing I wanted to do after the hectic week leading up to to the wedding. I needed the rest. It might have been the 90 degree Mexican heat, but we were in bed by 9 every night.
Personally I would save Europe for a year or two down the road when you are rested up and can spend a couple weeks travelling around. I'm not sure how long you have for a honeymoon, but I wouldn't want to go to Europe for less than 2 weeks and spend 2-4 days per city. It's a long way to go if you only have a week and even worse if you try to do London or Paris in a day or two to pack in a lot over a short time.
I went to Europe back in college (12 years ago) and went to Geneva, Venice, Paris, Amsterdam, London, and a couple smaller places over 3 weeks. All were good, but the best time was in Venice and Amsterdam. Paris had it's high points, but the people suck. Probably a must for a honeymoon. I've heard good things about other cities in Italy, but a couple guys that I went with got mugged by gypsies in Rome. If you get surrounded by kids holding up newspapers start swinging. We had a train pass which was nice and it took the place of a couple nights in a hotel, but I've heard there are plane tickets for less than train passes now. A night in a train compartment probably isn't how you want to spend your honeymoon.