Whenever I tell people I've seen all of Classic Who, the first question that I always get from interested parties (after they express envy or whatever) is confession that they don't know where to start. Conventional wisdom with the Classic Series is to watch what sounds interesting. Or start with the Hinchcliffe/Holmes era because those are the best stories. Or start with the 7th Doctor/Ace stuff because it's the most modern. Or you could be bold and start from the beginning (which a friend of mine is doing without having seen any of the new stuff. I'm still pulling for him).
My gut reaction is to give those curious an order that would popcorn through the whole damn thing.
Now I have one I feel comfortable sharing.