In developer interviews, the X-Com developers reference Dark Souls and Dwarf Fortress as examples of difficult games and as a comparison to X-Com's difficulty.
Dark Souls is a trial and error action game where mistakes are
punished with grinding to make up lost souls or backtracking. It's in no
way difficult in that it significantly tests typical action game skills
as found in series such as DMC, NG, or Bayonetta, or even God of War
and Vindictus, most of which have extremely fast enemies that require
millisecond timing, coordination, reflexes, and more
complex strategy. There's also far less potential for grinding out of a difficult situation. Yes, I can hear the goalposts being hurriedly moved at this moment,
claiming "Dark Souls is an RPG, you can't compare it to action games!" Most action games have RPG elements these days, including
all of the ones I just listed, and the comparison is valid.
It is true that you can theoretically run past every enemy in the game without dying, smack the final boss around a bit, then win the game. I don't think this is how Dark Souls is typically played, since it bypasses a huge amount of content. It's generally assumed that the player will want to explore the world and fight most or all of the bosses to experience the content.
has almost nothing to do with the strategic depth and difficulty found
in a turn based tactics game. Instead it piles tedium on the
player for making mistakes or getting caught by trial and error nonsense, although there is less trial and error than in Demon's Souls. Remove the punishment and grinding/leveling from Dark Souls and you're
left with a sluggish action combat game with bosses that don't take any
particularly complex strategy to defeat, certainly not approaching the
level of complexity that can be encountered in tactics games. Not to mention Dark Soul's lack of a scoring system and
pecking order style PvP.
Of course, that's one of the
reasons why Dark Souls is so popular. Almost anybody, even poorly skilled
gamers that are bad at other action games, can eventually complete it
with enough patience, tedium, and simple trial and error, then go around
proclaiming that they "beat such a difficult game". If
such gamers think they really do love difficult games, they should give this list a try and let me know how many buckets of tears they fill.
the same with Dwarf Fortress, which is a heavily random and punishing
sandbox game. Dwarf Fortress is designed for the player to randomly and
uncontrollably fail, and the randomized sandbox style method of failure
is supposed to be part of the game's amusement, much in the way that
random disasters in SimCity are supposed to be fun. You also need to
familiarize yourself with dozens of obscure rules and systems in order
to progress past the first few bits of game play. What does this sandbox play have to
do with turn based tactics game strategic difficulty or depth? Pretty much nothing, which is why it makes little to no
sense to be comparing X-Com's difficulty to Dwarf Fortress, either.