Methodology
I (gently) scraped all approximately 2200 games currently listed on Greenlight and extracted their genre and language options. I used language as a proxy for nationality here. Lots of games offer English and exactly one other language, so my assumption is that the non-English language is the native one of the developers. Games that only offered English as a language were counted as "English", and all games offering more than two languages were ignored.
Once I tallied the languages and genres, I also discarded all languages and genres that had fewer than 50 games. I didn't do an actual statistical test, so I don't know the confidence interval of the result, but with at least 50 data points per language/genre, I think there's something more than plain noise here.
Finally, to determine which kinds of genres are overrepresented for a particular developer language, I calculated the expected number of games of that genre and noted the deviation from this value.
Result
This is the resulting table, further reduced to show only genres where there's interestingly large per-language deviations. The values are games listed relative to the expected number, in percent.
The most definite result is that the Russians really love their horror games. They're also fond of racing games but have zero interest in platformers. The Germans are pretty similar but also like sports games a lot. Meanwhile, the Spanish and French both tend towards MMOs but sharply divide on the topic of horror gaming. Finally, nearly no-one outside of the English-speaking world is putting music games on Greenlight for some reason.
What does this tell us? Well, it's mildly diverting, and you can spend all day creating theses about the Russian national psyche to explain the horror game obsession...