This one is kind of difficult for me as most of the German cinema I've seen was during college studying Film and it was mostly Silent Cinema. I thought of the films I enjoyed the most, so Caligari didn't make the cut, on second viewing I could appreciate it but the first time, not so much. I'll stop the urge to go into my college self who really enjoyed studying Silent Cinema.
Goodbye LeninBrühl. A comedic at times family drama about Alex (Brühl) who wants to protect his mother from another heart attack after the Berlin wall comes down. It's about the lengths someone will go for someone they love, even so far as creating fake broadcasts and changing labels on food. The story was so simple and well executed. I know this usually appears in film lists but for me it was an introduction to another country's film industry.
Mostly Marthahere for further reading.