I think it largely depends on what you're interested in and what your native language is.
For fantasy, the genre leans very English-centric because it was invented by Tolkien and C.S. Lewis, or if you want to take it back to brass tacks, Edmund Spenser and the Fairy Queen.
That's not to say other languages don't have fantasy, notably the Witcher series in Polish or (I'd argue) the Night Watch books in Russian (dark fantasy).
If you can read Polish or Russian, I suggest both those series, if you can't, well, they are translated into English. :)
I think that's the brilliant part of learning English, the best books get translated to English, but may not necessarily be translated into your native language.
For science fiction, I'd be LOST trying to read Stanislaw Lem in Polish or Roadside Picnic in Russian. No idea if any of that is in your first language.
Take a look at the Cemetary of Forgotten books series by Carlos Ruiz Zafon as well, translated from Spanish, or in Spanish if you can read them. Not really fantasy, more like gothic romance, all quite good.