I have travelled a lot and agree with Brazil and Argentina. Indeed, much of south America. We cruised up the Amazon as far as Manaus and went to the Opera House there. We cruised around the coast and were blown away by the cities. Cruising makes sense as the oldest cities were founded when settlers arrived by sea. Although Machu Pichu does require an inland detour; it would take a long time to see everything. Going through the Panama Canal was a fascinating experience - it's not a cut through the land, like Suez, it's a 'water bridge', ie you go up from sea level through a flight of locks, cross the isthmus on a lake, and down to the other sea through more locks. The history of its building is a great, but long, read (The Path Between the Seas).
There is a huge variety of scenery, wild life, land use, etc in Australia and New Zealand, but there's a lot of distance to cover.
India is amazing but quite hard work.
The biggest pleasant surprise to me was Jordan. Incredible scenery, Petra, great Roman remains, interesting towns, with signs of a lot of different cultures, seaside resort, desert travel and stays, fern-lined gorges formed by warm streams, delicious food and welcoming people. But easier to do on a tour than independently.
I found Japan very clean, pretty and efficient and unusual to my European eyes but a little disappointing.