I've added a basic example for map based games to http://www.luaplayer.org/tutorial/index.html . Now it is trivial to implement games like Pac Man (one day) and easy to program games like Bruce Lee (less than a week). Some more ideas: http://www.df.lth.se/~ola/c64games.html
Some of this games were really fun back in the old days and even today. Today games have nice 3D graphics, but sometimes I miss novel ideas and good game play. Maybe I'm just too nostalgic :-)
A bit more difficult would be games with scrolling, like Boulder Dash, Marble Madness or Wizball (interesting game idea). But with 4 offscreen images and incremental update of parts of the images it should be really fast.