Zelda 2 is not a bad game. It's different, but not bad. It's actually quite fantastic for what it is. The hate on it is not justified.
Is the difficulty curve kind of insane? Yes. Is the final boss nearly impossible without cheese strats? Absolutely. But there is a reason why the term "NES hard" exists. It's a library full of hard games, and I wouldn't put Zelda 2 on or even near to the top 10 since you can grind for stat boosts if you really need to.
Compare that to something like Dragon's Lair where most players can't even get off the first screen without memorizing every nasty little detail and coping with horrendous controls. Friday the 13th and Goonies 2 both have maps that you need to rely on and are absolutely befuddling. Battletoads at a point starts throwing stuff at you so fast you can only just barely react and the two player mode makes everything so much harder because you can team kill and one player's failure is both player's failure. I could go on, but do I really need to?
You kick ass
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But I'd trade all my tomorrows, for a single yesterday