I have to go with Sweden. It's definitely a question of quality vs quantity, but Sweden has the best quality other than the US, China, and maybe Japan. Helix is top three, if not the best in the world in my opinion and Wildfire is easily top 10, and maybe even top 5. Also Balder, Twister, Lisebergbanan, Kanonen, and Insane offer a pretty good supporting class.
Germany has quite a few high quality coasters (EGF, Blue Fire, Karnan, Silver Star, Colossos, Flug) but you can't beat the Helix and Wildfire duo.