I think they are all worth seeing! My faves, in order of preference:
1) Impressions De France - This is, IMO, nothing less than a sublime masterpiece. The combination of French classical music with the gorgeous scenery is perfection. A major highlight is the combination of Debussy's sublime "Clair De Lune" with scenery of the French Alps, which gives me goosebumps. Revel, Satie, Offenbach, and of course, Saint-Saens are all well-represented in the musical score of this stunning film. Disney musical legend Buddy Baker always seemed to pick exactly the right music to go with each scene in this film.
2) Reflections Of China - Also has gorgeous scenery and a great score written by noted Disney park composer Richard Bellis that features nice Oriental motifs. This film really captures nicely the atmosphere of China's famous landmarks, gorgeous scenery, and bustling cities.
3) O, Canada - recently redone with a more comedic approach featuring Martin Short. This version has grown on me some, and I do enjoy it now about as much as the original version. I do miss the slightly longer runtime of the original, in which some of the scenery shots lasted longer and were not as quickly edited. Still, the current version does capture the beauty of the Canadian outdoors as well as its cities.
4) Spirit Of Norway - this is also a well done film with some nice views of Norway. Due to it's short run-time, it is not as in-depth as it could be, but what IS there is very well-done, and IMO deserves to be seen. I think the film compliments the ride nicely. While the ride focuses more on the fun fantasy of trolls and the cute Nordic wildlife of puffins and polar bears, the film is a nice, short travelogue depicting the people and places of Norway. Taken together, both give a better appreaciation of the nation and its history than just doing one or the other. I don't get the people who are in such a hurry to get out of the ride that they skip the movie. Look at it like this: even if the film were the ONLY attraction in Norway, that's STILL one more attraction than what can be found in Germany, Italy, Japan, Morocco, and the UK!