Well Ana, the most beautiful country, naturewise, I have been too is undoubtedly the USA, the enormous diversity of places like Yellowstone, the Grand Canyon and other canyons, Death Valley, the coast line between LA and San Francisco. I also like the wideness and the feeling of freedom that you have there as a tourist, riding with a rental through wide open places, starting in the early morning in the California mountains at a temp of -/- 6 degrees celsius and in the afternoon crashing in Death Valley at over +/+ 50 degrees. New York is also a one of a kind town, very impressive.
On the other hand in the USA and especially in the cities, you notice an enormous lack of cultural history in comparison to Europe. Cities that are built in horizontal and vertical lines and also the enormous kitsch-effect, the enormous amount of commercialism, the lack of 'natural' centers of cities.
I don't know if it's the right description, but there is also a lot of 'fakeness' in the States, people, who act friendly, but it seems a jobtrade, not a natural thing, and in conversations with Americans, I also almost always recognized an enormous lack of knowledge and even disinterest in anything not American ("You're from Holland, is that in Minnesota?").
The other country I want to especially mention is Kenya. The week that I spent of safari was probably the best vacation I ever had, the exceptional fauna of Africa is something I will never forget. What also sticks to my memory from Kenya, but not in a good way, is the poverty!! I've been to other third world/less developped nations like Mexico, Brasil, Sri Lanka, Turkey, but nowhere was the poverty as striking as in Africa. If you have seen that, well I won't say you will never complain again, but you sure feel blessed (and this from an atheist) for being born on the good side of the track (world). If you've been to places like this, you know that there does have to be some redistribution of wealth on this planet, but this is also extremely difficult, with the inherited corruption in countries like that.
The friendliest people I met in Turkey, the most arrogant in France, in Sweden the people were almost 'raw', very much living 'carpe diem', also you experience great differences between people from sunny countries and those who regularly have to deal with rain or even colder temperatures. Not only do southern people live more on the streets, but they are much more laid back, appointments are made on a maybe-basis, when I have the time I'll come by. In Western Europe and the USA we live by the book, in this case not the bible, but our agenda's, we plan things, we are a lot less spontaneous, not only on a day to day basis, but also on the long run. I've met people in other countries, who worked for a year, took free for a time, and when the money was gone, went back to work. Well that's just some of my impressions, maybe one more thing, the spirituality of budhism on Sri Lanka also made a big impression on me, not that, in your face attitude of Christianity or islam, but trying to find your own Zen, letting go of the materiality of the west. I am not a religious person, but this did appeal to me.
Also very nice places to visit: Scotland's highlands and Edinburgh, Croatia (a paradise on the mediterranean), Paris and Berlin (very impressive cities), the Alps in central Europe, Rio de Janeiro (although the guides told us that the Brasilian cities criminality was something to be very worried about, same applies for Kenya's capital Nairobi, as well as San Francisco by night), San Francisco, Vegas (the ultimate kitsch), diving in Floridean waters, Sea World, the waterfalls of Foz de Iguacu as well as the USA and Canada, the Canadian Rocky Mountains and the Pantanal in Brasil.