If there is something that is always indicative that I like a game, it's that I bother making an attempt and/or defeating any optional difficulty setting the game may offer. Sometimes it may just be the hardest difficulty, but at other times it's usually something that goes beyond that, and is only unlocked upon beating the game once or something. However, these optional modes can often vary in quality, and in perceived cheapness, so I want to know; which games featured the best or worst hardcore modes? (Games with just regular difficulty settings can also apply).

I'll get the ball rolling with three examples.

Resident Evil 4 Professional: I love this mode, it is fantastically balanced and creates differences that go beyond upping enemy health and damage. Bosses remain largely the same, and some cheese tactics are still possible (such as playing jumping jacks with Krauser on a ladder), but the main enemies of the game are way faster to react and close in on you. There's a reason this mode is locked until you complete the game at least once; it demands you to know what the layout of the game and it's levels are, as well as your own optimised upgrade route. Plus you unlock a laser cannon by beating this.

The Evil Within Akumu: I liked The Evil Within enough to begin a playthrough of this mode, but holy shit. It's whole gist is basically that everything kills you in one shot, meaning that you are perpetually one slip-up away from death. It seems both lazy and cheap. It does force me to consider the whole environment, and actually use hay bales to ignite enemies, so mission accomplished, I guess? The game just does not feel as though it was made for a mode like this. Still going to try to complete it.

Bioshock Infinite 1999 Mode: Played this through to completion as well. Hey, do you like being perpetually behind cover and never making any daring moves ever because every enemy absolutely shreds through you? It basically ends up just being a 'super-hard' difficulty, rather than actually adding anything new to the experience, as was claimed by Irrational. The fact that gear drops in Bioshock Infinite are randomised every time means that there is also 0 overall strategy to game progress. You better just hope you get the shield pants sooner rather than later.

I loved the Hardcore mode in Fallout: New Vegas because it added more to the mood and the mechanics without feeling restrictive.

I hate super hard and permadeath modes though because it leads to boring and overly cautious gameplay that isn't fun.

The only thing that comes immediately to mind is Bayonetta. The Climax mode is really cool, because it takes away your constant slow motion option. After beating the game twice, you now have to use everything you know about your enemies to beat them in REAL TIME. Great idea!

But you knoooooooooow, its fucking haaaaaaaaaaaard. So for many it still comes down to cheesing. I like the idea because its theoretically possible, but hard as hell. I'm just not good enough to do it properly.

I hate high difficulties in shooters, it always just comes down to excessive hiding and trying to cheese the AI.

I may be an outlier here, but I LOVED 1999 mode. I even got the achievement for beating it without purchasing any health from the vending machines. It just made every encounter a white-knuckle affair of pure balls to the wall killing time.

As for answering you question, I will say although it technically might not count: Call of Duty. Hardcore mode is the only way to play!

I thought Dead Space 2's Hardcore mode was an enjoyable challenge, and certainly made the game even more intense. Despite it being set on the Survivalist difficulty (which was the difficulty i played it from the get-go) the anxiety of knowing that if I die it's back to my last save made it much harder than I would have usually found it. In fact my Hardcore playthrough was the only playthrough (including a Zealot run) where I died against the end boss.

RE4 on Pro mode still isn't very hard, certainly not when put against the more gimmicky difficulties you mentioned, but it does make for a fun balance overall of giving you a hefty challenge without it feeling too punishing. It's at the very least much more preferable to the completely BS pro mode in RE5.

Oh, as for worst I think Gears of War 2, 3 and Judgment's 'Insane' mode is so unfair. Not only are you extremely fragile, but having the game end should you die without any opportunity to get revived wasn't fun at all for me. It was better in the first game where it was simply harder, but still featured the revive mechanic -- in coop anyway.

Bulletstorm. Playing it on the highest difficulty ruined the gameplay for me. Normal was perfect because it was a great balance of being able to experiment with the kills but it wasn't a cakewalk. Hard mode just turned it into a regular cover shooter because it was so easy to die out in the open.

Halo has great "hardcore" modes the hardest begin Mythic meaning Legendary difficulty with all Skulls turned on.

I like how customizable the difficulty is in Halo since you can turn on/off skull to make it just as hardcore as you want it.

So, the final 24 races of Ridge Racers on PSP state the odds of winning the race. They range from 1/100 to 1/200000 depending on the vehicle class. There are 24 tracks and each track has one of these very difficult races. The second last one was on my worst track and it took me 5 months to beat it. The rubber banding is just so insane. You need to block the opponents and have them smash into you to get enough speed to win. It's so bad that your average speed will be higher than your car's top speed. I had (maybe I still do) replay files from about a dozen races of me finishing last, despite being less than .010 seconds behind first place. I really fucking hated that track. I had figured out how to manipulate the AI at some point during the previous 22 races so they weren't really the issue. When I finally beat it and made it to the final race I was able to beat it in one try.

Edit: Oh, and those last 24 races are the only ones that don't unlock anything. It's all for the bragging rights, so this is me bragging about it.

I really enjoyed XCOM's hardcore mode. If you encountered bugs though it could be infuriating.

Halo's Legendary mode immediately pops to mind. Apart from some snipers in Halo 2, I always found it was the right kind of fun. Also, Hitman: Blood Money on Professional is simply amazing, even for your first playthrough. No saves forces you to actually roll with the punches and can lead to some pretty amazing runs where things go wrong in just the right way.

The worst ever for me is Veteran in Call of Duty: World at War, especially at the Reichstag. There can be one enemy hiding in a closet a mile away, but the game will still spawn 12 grenades on and around your position if you stop moving for even 3 seconds. And that's not even mentioning the instances of respawning enemies. Actually, the Call of Duty series in general sucks on veteran.

I really liked playing through Mass Effect 2 and 3 on insane. Did it multiple times (my favourite series of current and last gen). The biotic/tech combo's really become important and the game becomes a lot more tactical once you don't just mow through everything with a single power usage. Also basically all enemies will have barriers, shields or armour so planning ahead to deal with all the damage resists becomes pretty important.

Normally I hate permadeath, but it's the only way I can enjoy Dungeons of Dredmor. I love how attached I get to each new character I make.

There's also obviously Doom played on Ultra Violence, pretty much the only way to play. I once did Doom 2 on the Nightmare difficulty setting, but I kept on running out of ammo and wasn't sure if I enjoyed it or not. It did make me feel like a big man though :D

The Devil May Cry games' Dante Must Die mode is usually very fun and balanced. In this mode the enemy layouts change and they sometimes get new moves, including the ability to turn on Devil Trigger themselves.

I've also enjoyed playing some of the Silent Hill games with the puzzle difficulty turned up. They actually change up some of the puzzles to be more complex.

Shadow of the Colossus's harder difficulty also changes up the weak points for every enemy, which was pretty interesting.

The Max Payne games' New York Minute mode is pretty dope too, forcing the player to complete every level within a minute, with each kill giving you more time to complete it.

Advance Wars' Hard mode is also pretty cool, as it actually gives you new missions to play with.

Oh and Resident Evil Remake has this mode in which all the enemies are invisible. And there is also one in which a zombie follows you throughout the mansion, and you can't kill it or else the game ends.

the hardmode bosses in the ulduar raid of world of warcraft were really cool especially the one where to activate it you pressed a big red button in game, but they really did some work on changing the mechanics of the fight instead of just increasing numbers.