MattRat VS Hagane: The Final Conflict (Super Famicom) 

The games you mention being harder than Hagane, overall I agree, after all, these games has a fair share of trial and error, but some games (like Battletoads) really need a lot of practice compared to others to be beatable to some extent, not to mention that probably you end up finding your own exploits to these games (like how I do it with Bayou Billy to decrease the odds of having the enemy hitting me after they take a hit by a large scale... and it took me learning how much the attack animations of Billy last so I could time the hit when the attack animation is ending when the enemy aproaches me so they take a cheap hit instead). Sure, for me some of those other games you mention might not qualify as hard for me (like Return of the Jedi... a game that from time to time I pretend is the original Super Star Wars and do a full run pretending that I don't have the luxury of the Passwords as how said game was) but I can't deny that it's hard and it's place on the hardest SNES games is deserved. As for Hagane itself... I REALLY should give this game a try, not to mention that I'm planning to revisit some games that I played in the past that I liked it but are kinda obscure... like Twisted Tales of Spike Mc.Fang for example.