I posted this in the Comments section and I actually did some research for it, so I thought I'd post it up here too.
I'm assuming that the more money that is spent on books in a language is an indicator of the strength and influence of that language's culture(s)--that is, the bigger the market, the more competition there is, and the more competition there is, the higher the average quality of works in that language is going to be. Thus many works are translated from English and few are translated from Cambodian.
It makes sense that since many more quality works originally in English are available than in any other language, there's not that big a market for foreign books in translation in English-speaking countries, and only the very best get translated to English.
However, in a country like Finland, which produces many fewer original works in its own language, there's going to be a much bigger market for translated books, and I bet at least half of them are translated from English.
According to El Pais Anuario, of the ten biggest bestsellers in Spain in 2002, six were by English-language authors (Tolkien, Ken Follett, Katherine Neville, Arthur Golden, J.K. Rowling, Noah Gordon). They also have a list called "Most Read Authors". I have no idea how they calculate that, but Stephen King and Frank McCourt are on that one, too.
That is, the English language produces many very professional high-quality books aimed at the lowbrow-middlebrow audience that are translated to languages around the world, just like it does in cinema. No other language does that. Middlebrow-lowbrow works written in other languages are not translated to English. Why should we read foreign crap? Our own crap is better. We only translate the very best foreign stuff.
Note that none of the abovementioned authors exactly form part of the Western canon. The more prestigious American authors--Don DeLillo, Philip Roth, Saul Bellow, John Updike, Thomas Pynchon, Richard Ford, T.C. Boyle, Cormac McCarthy, and the like--are not bestsellers in translation in Spain any more than they are in the States.
Miguel de Cervantes is also on El Pais's "Most Read" list, which is why I take said list with several pounds of salt.