6: Canada, Mexico, Germany, Austria, Switzerland and France.
Favorite: Austria. I have exactly zero bad things to say about Austria.
Least Favorite: This is complicated.
Which country did I enjoy the least? France; We had two days in Paris at the end of a two week trip, the weather made everything dull and grey, my wife was getting over a cold, I had the flu and we were both exhausted so I don't think it's fair to judge France on that experience.
Which country did I think was the worst? Mexico. Holy shit Mexico. I saw beggars, pick-pockets, litter, corrupt cops, you name it but didn't have to directly deal with any of it.
Where would I revisit? A tie between Austria and France. I'd love to give France a visit beyond Paris when I'm not sick and the weather isn't blah but there is still a ton I'd like to see in Vienna, nevermind the rest of Austria.