So I've finally finished the first Zelda game. It's good that I had guides to help me find a few things which would have been tedious to look for. The last dungeon was starting to get into "too difficult" territory.
And in the same spirit, I've finished the first Castlevania. It's really good, though there are a few levels that definitely feel like they were made just to make the game harder. I've used saves to be able to "skip" parts that I was able to get around easily and before bosses, so that I wouldn't have to play an entire level over and over just to be able to learn how the boss works. It was still challenging but didn't get as frustrating as it would have been if I had been just relying on passwords.
Then I went on to the second game, with a few hacks to improve the experience (better translation, in-game map, hints for destructible blocks, etc.). Even with the improvements, it's still not as good as the others but it was okay.
And then I played the third one, once again with hacks. This time to get the japanese version (with the better music) with English texts and also to get better controls (control over the jumping, etc.). That might feel like cheating, but I'm glad I did or the last levels would have probably felt very frustrating (though the bosses are much easier this time). The multi-path approach is great for replayability, but I'm not sure I'll play it again soon.
I'll probably go on with Castlevania 4, Bloodlines and Rondo of Blood. I'm also wondering if I should give a hacked Zelda 2 a chance.