I agree on Sleepwalker. Although I've managed some levels, it really felt like they were overdoing it. At least there should have been some smaller introductionary levels which held a rather reasonable easy difficulty, but no... at once the levels were extremely big and hard to navigate through. I don't consider Sleepwalker being a bad game, in itself, but it is just that it is too much too soon.
With Kid Chaos I think the same is awfully apparent. In the second world there is this level which one should rush through, with little time and many flowers to break to be able to exit the stage. I know my Sonic. I really do. I've played them through many times and never had this kind of trouble... but with this particular level in Kid Chaos I haven't even managed to reach the end WITHOUT bothering about the flowers. How am I then supposed to reach the end while breaking the necessary amount of flowers? Maybe it is just me... but the game feels damn impossible because of this.
Oh, I then we also have Shadow of the Beast II. I it hadn't been for the extremely loooooong game over scenes and the extremely looooooong intro, one could maybe learn how to navigate through the game just by simply doing it again and again and again. I borrowed the original from a friend... back in the days when I had the patience to play games until I managed to beat them, no matter how hard they where, but I didn't get long at all. By the third or fourth time I got so fed up with having to wait like 10 minutes to be able to play for three minutes, that I just handed the game back to my friend and never bothered again (until a couple of months ago, when I just had to confirm that I hadn't been dreaming).