Obviously, being American, my experience is limited to research, heresay and, of course, my actual travels. I tend to experience the best of those countries (that I'm aware of) when I'm there, and I couldn't care less about their politics or issues that don't affect me while I'm on a vacation. So, here is where I have had the pleasure of going:
Trip 1 (England): London for 4 days then the Cotswolds for 3 days
Trip 2 (Italy): Rome for 4 days then Montepulciano for 4 days
Trip 3 (France): Paris for 5 days then Normandy for 2 days
Trip 4 (France and Scotland): Paris for 3 days and Edinburgh for 3 days
Trip 5 (Germany and Czech Republic): Heidelberg for 1 night (sister studying), Rothenburg for 2 nights, Munich for 2 nights, Prague for 4 nights
I doubt anyone cares, but that's my "background." It's REALLY hard to pick. Paris was probably my favorite city, as the atmosphere really "took" me and I loved just doing everyday things like getting coffee or going for a walk there. However, I think I had the most fun in Edinburgh, and I was really pleasantly surprised with how awesome it was. It's probably not fair for me to judge England, as I was pretty young and need to try to go back, and possibly the same with Italy (though I sitll have never been blown away by anything more than the Colosseum). Additionally, Prague was one of the coolest cities I've ever been to, but I think it ranks a notch below just because I wasn't as familiar with it beforehand, and a slight culture difference made it just a tad harder logisticwise; people were fantastic, though. In the end, I have to go with Germany. I'm probably a little biased given my family's German roots and that my sister was at least a little comfortable there by now, but the people were awesome, I actually liked the food, it was exceptionally clean and well-run and there's nothing more fun than drinking some German beer for this guy.
Scotland was damn close, but Germany by a hair.