Over an Concatenation (a very valuable resource), there is an article entitled Unseen Mainland European SF Classics which was “written as a precursor to the Euroconference Odyssey 2010 in London and a panel on this topic”. They highlight various works from France, Germany, Hungary, Portugal, Russia, and Spain.
Here’s an excerpt:
If you happen to frequent many of the various major international SF gatherings, be they in France, Russia, or wherever, the chances are that a good proportion of SF books in the dealers hall will be by British and North American authors. Indeed if you go to that very Anglophone of conventions, the SF Worldcon, then virtually 99% of the books on sale in the dealers hall will be in English by English-speaking writers even if their nationality is Scottish, Canadian or Australian, let alone English. What you do not see in British and N. American bookshops (outside of French-speaking Canada) that often are foreign SF/F books translated from another language. Yet all mainland European countries, and nations further afield, have a substantial history of SF publishing and many have had SF and fantasy classics that have sold well over the years.