Don Doko Don needs to be played via both players to maximize the pleasure. It is tough as there are a lot of unexpected enemy twist, etc. but I think after a few re-runs, it gets better. I'm liking it more and more. Great hidden gem.. I personally discovered it myself early last year after trying a ROM image of it, then proceeded to track down a copy
Another one I highly recommend is PUZZLE BOY. That game is awesome, obscure too. I got a beatup copy for $5. I like it so much I'm looking for a full complete copy to put in my perm. collection
I played Don Doko Don and Image Fight today. Both are tough games. Image Fight does so many cool things though, I'm surprised I don't hear about this game more often. Can't wait to get good enough to get deeper into the game. If the innovations keep up, this is an impressive title.