For no other reason than pure curiosity[*], I made the above comparison of spoken languages compared to land area. I started with Wikipedia's List of countries and outlying territories by total area and made a table of country vs. major spoken languages in that country (mostly official languages, though I made some judgement calls). Then using the Google Chart API, I produced the above graph, as well as an interactive page that shows countries by language on a world map.
Not surprisingly, English is the top of the list with several large countries. Russian is next just because Russia is the largest country, followed by Arabic, French, Spanish, Portuguese, and Chinese. This comparison quickly ends up being pretty meaningless because I can think of no other ranking that would put Kalaalisut (Greenland, 50 thousand speakers) above Indonesian (250 million speakers), except maybe latitude.
While working on this I thought of another potentially interesting comparison: Languages by tourism volume. On average, what languages would people need to learn as a "typical tourist"? (I'm sure travel language book publishers already know this.)
[*] Well, I also implemented this using Psil in a mostly functional programming style. This was an opportunity to use Psil for something non-trivial, as well as to experiment with building an HTML rendering system.