What games do I recommend? All of them! Seriously, there are very few bad games for the system. If you aren't hung up about having complete games, there are tons of cheap new loose games available on ebay. I think I got 1/3 of the system's library for like $30 in one auction a while back.
Also, to give you a little background on what you got, I bet your system and games come from one of those blister packs that they used to sell at Electronics Boutique after the NGPC went south. Basically, the boxes and documentation were dumped, loose (but new) systems and games were put in blister packs and sold for a discount, it was an awesome deal.
I really, really love the NGPC. I never play mine since it's too dark in my living room, and when I attempted to front light mod the system I messed up the GBA frontlight, so it's all kinds of fugly.