I´m German and I like watching lets plays too. There are many very good lets players in Germany and they have a wide range of games. If you like old games, you should go with PhunkRoyal. He was one of the first big German lets players. He is an amateur actor, so his pronounciation is very good although his voiceactiong sometimes becomes very weired. Another one with a very clear voice is Lightcatcher. He plays Zelda, Elite Force and Drakensang. HerrDekay is a very good address for Nintendo games. Cause, I´m German I don´t know how the subtitles are, but I´m sure you´ll find someone you can understand a bit, at least.
For games there is Gothik, as mentioned before. A newer one is Risen of the same developers. If you like City-planning games there is the Anno-series and the Tropico-series. I played Tropico 4 recently. You are a dictator of a caribean Island. The game has a very interesting setting and much humor. Your advisors have very strange missions. Nontheless, the game plays kinda slow and often you just have to wait. If you like old Scummgames like Maniac Mansion or Zakk McKracken, there is Maniac Mansion Mania. A German website where everybody can create own little Scummgames based on Maniac Mansion. These are called 'episodes'. Every episode has a play time of about 20 minutes, iirc. Every one has its own plot and its own riddles, as they are from various fans. Nontheless, there are many running gags and many hilarios ideas. At this time there are 88 episodes available.
Also I´d suggest you to communicate with Germans. Sounds hard, as Germany is much smaller then the US, but I think you could get a group together, to play games online or something. As far as I know, there are many Germans at this board.
However, I which you much fun learning our 'fantastic' language.