I personally love classic games more than modern games because of the difficulty, most modern games are much easier, there are some exceptions like Kid Icarus Uprising, the Devil May Cry series, or the modern Ninja Gaiden games but for the most part there isn't much of a challange anymore, never after those days was there another Sonic game where you fight the final boss without rings, never are hammer bros. a threat in Mario games, the hardest modern Castlevania title is Order of Ecclisia leaving the other modern Castlevania titles being some of the easiest in the series and not just because they've been using the Metroid-vania style for so long and games are overall very simple now, granted N64, PS1, and Dreamcast had a lot of easier games as well but at the same time those games had more of a balance between being easy and being hard which most games now don't do anymore, it seems to be making it as simple as possible to the point where there are forced tutorials that aren't needed because games back then never had tutorials and everyone was able to figure out what to do just fine, even with higher difficulty settings things weren't exactly all that hard and even if they are hard they're usually idiotic difficulties where you pretty much have to be perfect which was never the case in classic games.
What most people now a days don't seem to understand is that there's a gap between a game that's hard or a game that claims it's hard but at the same time is too punishing for it's own good and the best example I can give is with ROM hacks, I go on Sonic Retro from time to time and I download some of the ROM hacks from there, some of the hacks are meant to be harder versions of the actual game but more than half the time there are some really ignorent decisions like spike placements that you won't see until it's too late, bottumless pits in the same sense as the spikes, in the second zone there's a spring that launches you into a spike pit for example, things like that don't make a game hard it makes them badly designed and not fun, games that are actually hard are fun and the reason is because anything that happens to the player is their own fault, you're being tested on what you know about the game so far and use what you're given and if you either get impatient or decide not to plan your attacks then that's your own fault, a game should never be hard because of the fault of the game but the fault of the player for making mistakes because that's how you learn to play the game to be able to beat it and that's what I love so much about classic games because they do exactly that, that's just my view on it though.