What are some of the most difficult and challenging games you have ever played AND seen?
For me here Ori and the Blind Forest is currently and by far as well as without a doubt one of the most difficult and challenging games I have ever seen AND played in my gaming life but in a really good and fun way 
Mario brothers the lost levels, also zelda 2
The NES had some hard games 
Battletoads. That ā ā ā ā ā ā ā turbo tunnelā¦
The problem with Battletoads is that you have to avoid cheap kills early in the game in order to save your lives to get through the cheap kills later in the game. Everyone complains about Turbo Tunnel (itās where most people get and then quit because they realize they have better things to do than frustrate themselves on this honestly not very compelling game) but you can memorize that and itās always the same. After twenty years my fingers still let me do it no problem. Much worse, in my opinion, is the stupid descent in a string where random birds and robots will one shot you with semi unpredictable behavior where you are fighting the controls. I feel like Battletoads is hard in a bad way, as versus challenging.
Ori is challenging, in a good way. I had trouble with a few places but it didnāt seem all that hard to me. And unlike Battletoads, the payoff is worth it to see the beautiful game.
Ninja Gaiden on NES was a hard game that I basically memorized and could beat without losing a life back in the day. The 3D reboot on Xbox was reputed to be hard but I wouldnāt say it was. The original PS2 Devil May Cry I thought was much harder. Took me forever to beat the stupid Spider.
The original Donkey Kong is famous for being difficult and random. Alien Hominid HD (which you can get on BC) is hard as hell.
Challenging but rewarding games I can think of are Overcooked, X-Com, any of the zillions of Roguelike games you can find now. Bravely Default on DS and all of the Monster Hunter games.
Well, thereās always the Souls series and its contemporaries. Dark Souls, Demonās Souls, and Bloodborne are all built around the same basic principles, but the Dark Souls series in particular incorporates its design philosophy into gameplay. Itās built around trial and error, and forces you to play at a slower pace to avoid dumb deaths. It knows you will fail (often repeatedly) and is both plot and gameplay focused on the aspect of learning to accept failure. After a while itās not longer super difficult, and New Game Plus, while more challenging, is much less of an issue now that you have good equipment and knowledge of whatās to come.
Doom also comes to mind. Doom and Doom 2 had some pretty insane levels when played at a higher difficulty, which were only made more frightening by the Brutal Doom mod in most cases. But the new Doom (Doom4) has its own insane challenge; Ultra Nightmare mode. The campaign is bumped to the highest difficulty, where enemies can kill you nearly instantly, ammo/healing items are incredibly limited, and best of all you only have one life. Death deletes your save file and places a progress marker for your friends to see, and to remind you of your failure.
Otherwise thereās plenty of older games that really pack the heat, either for difficult level design or poor game design. Things like Battletoads, Fantasy World Dizzy, Sabrewulf, Teenage Mutant Ninja Turtles, and many others had their own challenges, though theyāre only a drop in the bucket of difficult old games.
F-Zero GX Story mode made me rage quit so many times.
Spelunky is pretty hard until you figure out the level patterns and techniques required to do well
I loved Ori, but being more of and old schooler I didnāt have a lot of trouble (until that level where gravity changeā¦My God! It was hard before in Sonic games and still is xD).
Iāve played many games during my chilhood, games I used to rent too, but liked my own games too (like invisible achievements, that could be dying as least as possible, not continuing, not using certain items or collecting items I was supposed to use)
For instance: I loved the challenge to play Adventure Island 2 , Island 8 (final Island) with no items at all, and playing the last level just dodging enemies and obstacles (no weapon at all) which requiread nice timing.
Older games I find challenging to play were Contra 4 (NDS) and Dracula Chronicles X (PSP). There are few games now that get my attention or will make me so eager to playing them to feel what I felt for those games or the games after them.
These were just examples =)
F-Zero GX on the Nintendo Gamecube. That was the HARDEST game I have ever played and fully beaten, 100%. Itās a lot of fun and has great character, music, graphics, and gameplay, but damn is it hard.
GHOSTS. AND. GOBLINS! (nes)
nuff said
Super Ghosts and Goblins wasnt easy eitherā¦
Too be fair though to all the NES & SNES games mentioned, back in the day games were way shorter and in order to lengthen the experience they were simply made very hard to finishā¦also, no quicksaves, etcā¦if you were lucky you got codes, like the megaman gamesā¦
True, but at least that one was a bit more manageable thanks to improved controls and the armor upgrade system.
Kids these days. They say Dark Souls is the hardest game ever when they have absolutely no idea of the struggle of the late 80ās-90ās games
Yeah I dunno, you address it in your post but Iām really not sure I would call the souls games āhard,ā more like very punishing for mistakes but entirely manageable other than occasional difficulty spikes. Itās actually one of my bigger gripes with the series, as its bigger āroadblockā bosses (e.g. capra/O&S in DS1) are often not very good fights. Some people complain about DS3 being āeasierā but I just see it as them learning from mistakes made in earlier games, with the end result being some of those difficulty spikes getting smoothed out.
More on topic though, Iām pretty sure I never even finished the first level of Volgarr the Viking. That game is something else.
I tend to agree about DS games. If you play them cautiously, you can go through and very rarely die. Itās just slow and drawn out to play that way - and (I know itās blasphemy) but I just get bored. I keep trying to get into them and I never really do.
Well, you CAN play them very quickly, itās just more risky. Once you know enemy placements and what you have to fight vs what you donāt you can really go nuts. Trial and error slowly inching forward for the first playthrough, and hyperspeed blitzing through the level for everything after that.
F-Zero GX was a pretty hard game - the story mode in particular was pretty nasty. Awesome and extremely fun game though 
Hardest game I ever played? Dino Ricky on the NES. Eff that gameā¦ 
Hardest game I have ever played is beatmania IIDX.
After 2 years of playing very regularly (and I am very good at music games), I was still nowhere near being able to play the hardest songs in the series.
Getting good at IIDX takes years and years and years of practice.
For more ātraditionalā games, āhardā can have lots of different meanings. Beating Riven without a FAQ was very hard (but Iām very proud to say my friend and I did it together)ā¦ a lot of people just give up and look at the answer. But once you know the answer, Riven is not hard. There are technically demanding games (ie, even if you know what to do, actually doing it is still the hard part), and I think this is probably the traditional meaning of ādifficultā in games. You could point to a number of annoying NES games that were poorly designed and theyād probably top the list here. Stuff like Ori and the Blind Forest, fantastic game though it is, doesnāt strike me as very hard, even though I died 100 times. The punishment for death was small and it felt pretty clear that I would conquer any part in that game with a few more minutes of practice.
I canāt remember any game that was so incredibly difficult that I just gave up and never finished it. But I probably just havenāt played the right games. Iād say Spelunky (and some similar roguelikes) would rank as one of the harder games Iāve played over the last decade.
Especially that stage where you basically reliving the movie Speed
Lol. I donāt actually remember hardly any of the story missions in the game - I just remember it being hard. The two hardest levels from my recollection were the one where Samurai Goroh tries to blow you up in the canyon (that level seriously made me quit story mode for a while ), and the final on Rainbow Road. That level was just so long, and the bloody thing didnāt have any rails for the whole duration 
Angry Video Game Nerd Adventures. Itās a shload of f*ā¦just kidding. Itās really fun. That game is tough, but in a good way.
Also The Impossible Game. I played it so much I have nearly the entire original stage memorized, but Iāve only made it through once.