Definitely the restrooms in Japan are the best in the world. Clean, well maintained and everywhere. Scribbling is everywhere in Europe, even in toilets at airports but very rare in Japan, especially in private properties - airports and shopping centers.
There are information panels at Haneda airport in Tokyo showing the vacancies of the restrooms. If the nearest toilets are occupied, you can check how far is the other toilets.
One thing I do not understand in Europe is that number of wash basins are more than the number of urinal. I think it is better to make more urinals and toilet booths rather than the wash basins. People can wait to wash their hands but sometimes cannot wait for the urinal or especially to sit on the toilet bowl.