The Spanish language is actually incredible, in terms of literary output - far greater than Russian I would argue. There are reasons for the prevalence of Russian though, on these boards. over Spanish. My Guesses:
1) It is Russian novels, despite the short novel and short story being a major form in Russia, as it is in Italy, and France. English really is not the language of short-story writing, so people's tastes bend that way.
2) Dostoevsky appeals to an age group. The same 17-18 year old kids who discover Nietzsche or Existentialism and think they have uncovered the world seem to have a drawing to this kind of fiction, as the bitter filthiness contained within these texts, and the rather harsh, misunderstood philosophy, mixed with pessimism, fits nicely with the hormonal swings of adolescence.
3) Who here ever hears about Spanish literature, that is, classic or good Spanish Lit?
4) Dostoevsky, in circular reinforcement, is promoted and shelved according to the top list, creating a situation where reputation feeds reputation, meanwhile other works go ignored.
Still, I wouldn't mind a discussion on Gypsy Ballads or something.Or even contemporary or classical verse, if someone is up for it.