Korean: Best for crime-suspense-thriller (after that slice of life) Chinese: Best for Art, action (after that slice of life, romance) Japanese: Best for Slice of life, violence, weirdness (after that romance, thrillers) Indian: Best for mindless fun European films: I don't have much experience but I tend to like more French and Italian
I chose French but I was stuck in-between that and Spanish. I really like Guillermo Del Torro's stuff and I know a little Spanish and want to become fluent. But right now one of my favorite tv shows is Les Revenants which is a French show. I've also seen some other French movies which I liked, so I guess that's why. French is my first, and Spanish is my second.
There are plenty of great foreign films out there from various countries. However, I have to say I love the work being done in Korean cinema. It's a little easier to get into thanks to all their western influences, but they still have some stellar stuff. I highly recommend seeing Oldboy if you're into gritty revenge films.