Russia's creative output seems to me to have been disproportionately large
in the last ~150 years. Consider :
Aleksandr Pushkin Aleksandr Borodin
Nikolay Gogol Modest Mussorgsky
Ivan Turgenev Nikolay Rimsky-Korsakov
Leo Tolstoy Peter Ilich Tchaikovsky
Anton Chekhov Sergey Rachmaninoff
Maksim Gorky Igor Stravinsky
Mikhail Bulgakov Sergey Prokofiev
Boris Pasternak Dmitry Shostakovich
Not forgetting the Ballet Russe
and Sergey Diaghilev and Vaslav Nijinsky.
This seems to me to be an awful lot of very high-profile
creativity for one nation.
Even if you take into account its population of around 150 million,it still seems quite a lot. Perhaps a country that had a system of institutionalised hardship might expect this, however, people are more inclined in such a situation to create work criticising the status quo with varying degrees of subtlety. Another factor might be the lack of availability of mainstream entertainment media and other luxury distractions that others take more for granted. Stifling of freedom of speech, something that's been fought for so hard for such a long time, would also enrage more strongly morally minded people to express themselves creatively. As Professor Pi points out, many athletes, ballet dancers, and musicians would have been highly motivated to succeed by the prospect of escape (however brief) under the Iron Curtain.