Xenophobe is very playable. But just like a lot of 7800 game it just seemed to not be complete. It's missing characters, missing certain elements from the arcade, a lack of direction - no real ending or goal.
Karateka is just a half-assed game all around. Missing a lot of elements that made the Apple, C64, etc. conversions a classic. And when you look back, there really isn't a reason why these things are missing? The creators cut out all the things that made the game edearing. For me it was the cut scenes. Like when you're running toward the castle and it cuts to one of the enemies running toward you, building suspense. And the controls are hideous....