Interesting list! It doesn't correlate too horribly with how I feel about prog either, but I'm a bit puzzled by some of your placements regarding influence and popularity. For example ELP has sold over 35 million albums which I think is a lot more than Genesis did in their proggy years. A lot of the Canterbury bands, even the most popular ones like Caravan, comparatively had little success and is revered by a minority, yet rank much higher than for example Kansas who, whatever you might think of them, represent a big chunk of 70s american prog and has had international hits.
So it's a reasonably good list over what I like, but I think influence is debatable. Do you mean influence on people in general or just influence on those relatively few who like prog?
edit :
And if it's about proggers influence on prog, why rank f.ex procol harum lower than Gentle Giant? Procol harum lower than Caravan?