So I beaten Shatterhand, and I then I played it 20+ more times. The game is great fun, controls well, has good to great music, and good graphics. But this game is barely challenging, only the falling rock section, fire rising up section and the last section of the last stage were what I found difficult and even after some tries you can get through them. The bosses are just too easy and you can tank some of them, like the final boss even, which I beat on my 2nd try when I 1st got to him. In one of the runs I did I didn't get hit by the final boss even once!
I remember this being compared to Journey to Silius in difficulty and before I even played the game I knew Journey was harder. And it turns out I was right(IMO), like this game is not even close to Journey in terms of challenge. The robot helpers, full health stations, mostly easy enemies and bosses, mostly reasonable difficulty with easy and hard bits, unlimited continues vs(Journey) a game with extreme limited health items that barely heal you, mini bosses that are tougher than most of the bosses in Shatterhand, no bosses that you can tank(tanking is suicide in this game), a difficult platforming stage at the end that scrolls the screen over, having to fight 2 final bosses on one health bar, and best to use the required weapon or else you're in for a long fight, and 3 continues. Journey is quite harder in terms of difficulty.
Overall Shatterhand is an awesome game that's enjoyable and a blast to play and is one of the better NES games out there, but it's far from the hardest, and not even that hard for that matter, still, it's a great game that everyone should try out.