The C64 game was a lot more cerebral and was almost certainly the more notable game of the two when first released, breaking some new ground and having a lot of ideas in it, but yeah, this one has aged a little better I think. As Chris says the game is very accessible and actually can even be pretty exciting at times due to the strict time limit and sparse health pick-ups. Graphically this is especially impressive for the hardware, representing possibly the best visuals yet seen at the time. Where it comes to unfairness, personally I don't think I can criticise the game in this area as I'd say most titles from this time, bar the odd NES release, were generally even less reasonable than this. Obviously the best action-adventure games of the time were coming from Nintendo during this period and there's no way the game can beat out the likes of Metroid, but even so its well above the average for the release year.