I used to play the SG-1000 a fair bit in emulation, and I enjoy its library. Some of the games are mediocre at best, but it's got a very good version of Chack'n Pop, and Ninja Princess is good fun too. Not coincidentally, I translated both games (though Ninja Princess is a bit of a hackjob).
I like the idea of Hustle Chumy, but it seemed way too easy as far as I could tell. There was another game I could never get anywhere with...C-So, I think?