In reply to no_more_scotch_eggs:
I guess if you value it against the size of the country, the sheer variety of Scotland's scenery gives it a strong case. Coast, hill, mountain, woodland, rivers, lochs, green border valleys, moors, islands, beaches, rock towers, bogs, etc, etc, it has it all.
In fact, the whole British Isles is remarkable for the variety of beautiful terrain in a small place. Its just too full of us people at times. I still argue that even in the crowded south east, you can find solitude and quiet beauty with remarkably little effort though.
Outside of the Home Nations, limiting it to places I've visited, the USA has to be up there with so many of the most amazing places, such as their many National and State Parks. Personally I have an affinity for the Scandinavian countries, and for beauty, Norway would probably win as I'm partial to pointy peaks and exciting coasts. So Slartibartfast's award for Best Coastline would definitely have got my vote. Iceland is arguably my favourite country, but I'm not sure I'd class it as being for beauty, as opposed to how spectacular and bonkers it is!
Places I haven't visited but look stunning would definitely include New Zealand and Chile.