Over the course of last week and this one, we're bringing you our pick of the games of the generation. Today it's Dark Souls.

I haven't played Dark Souls for over a year, and anyone who has played it extensively is going to find it infuriating to discover where I am: I'm at the end of Sen's Fortress, just before the fight with the Iron Golem. I know! I haven't even made it to Anor Londo yet and it's right there! I'm not stuck. I just haven't done it yet.

Perhaps that's because I'm slightly intimidated by Dark Souls, even after the 25 hours it took me to reach that last bonfire before the rooftop. When I arrived at Sen's Fortress, I felt strong and confident. I had survived Darkroot Garden and Midnight Butterfly, Blighttown and the Depths, Gaping Dragon and the Capra Demon. I had spent an entire day grinding for XP in the Undead Burg, listening to NPR Planet Money podcasts on my laptop. (I have no idea if the former was wise or not, but the latter is always recommended.)

As I walked up the Fortress steps, past the spot where I had once encountered an onion knight (not to be confused with that impostor in Game of Thrones), I thought I would be overmatched for whatever lay within. I didn't kid myself that I had out-levelled the rest of the game - I knew better than that, at least - but I was hoping for a bit of respite. Maybe a couple of hours where I could let my concentration slip and coast a little.

Dark Souls' combat is based on the idea that medieval weapons are heavy. It could carry entire games, but that burden is shared here by so many other brilliant things. (P.S. Screw this guy.)

I can't remember if it was the first Serpent Soldier I encountered who pasted me all over the floor, but if it wasn't him then it was the arrow trap I didn't notice I was triggering as I panicked at the sight of him. Next time, I made it past this room onto a narrow walkway punctuated by swinging blades. I was sent flying into the gloom below either because a hidden Serpent Soldier came running at me and I lost my footing, or possibly because I was knocked back by the Mage casting lightning spells from a distant platform. I can't remember which of these fates befell me first, I should say - they both did for me at some point.

Either way, I fell into The Pit, home to four Titanite Demons. I had run into one of these guys before, in the large room next to the bonfire on the other side of the bridge just prior to Sen's Fortress. He blocked the path to Darkroot Garden and I used to run around him out of fear rather than taking him on, because he generally flattened me. Four. Now I would be avoiding these guys as well.

I will go back to Sen's Fortress and persist at some point, not because I'm stubborn and bloody-minded (although I am), but because, believe it or not, I was having tremendous fun. Dark Souls is often portrayed as some sort of biblical cilice that we must all wear to atone for our love of modern games that play themselves, but when I finally made time to play it at the beginning of last year that's not what I found at all.

Critical consensus Oli Welsh reviewed Dark Souls when it first came out, awarding it 9/10. "If Demon's Souls was purgatory, Dark Souls is a descent into hell," he wrote. "From Software's follow-up to its celebrated dark fantasy ordeal is even harder, even more remorseless and bleak." By the time the PC version was released, Rich Stanton had seen it all, but he was delighted to keep playing, as he reported in our Dark Souls: Prepare to Die Edition review, also recipient of a 9/10 score. "There are some few entertainment experiences that rise above mere amusement, and the world of Lordran is one of them: an endless feast to be chewed over and digested, each morsel swallowed with lip-smacking relish before returning eagerly for the next."

Instead I discovered a game that rewards patience, concentration and experimentation, and punishes haste, carelessness and narrow-minded play. A hostile and cruel game, as Oli put it in our original review, but one that cannot be called heartless or soulless. Perhaps the reason I haven't gone back isn't that I'm intimidated - maybe I'm just ashamed that I thought my cheap tricks (grinding!) belonged in a game of this bearing.

Yeah, sorry about that.

Grinding's not even the worst thing I did. Shall I tell you about that? OK, so there's a sewer tunnel that runs out of Undead Burg back towards the Firelink Shrine where you encounter a woman who will sell you various kinds of moss. She is one of a small number of NPCs in the game and these people are precious, because if you kill them, even by accident, they will never return. The game doesn't care what that does to your prospects, or how many hours you've put into your single save slot; you stopped concentrating.

Well, I stopped concentrating there, and I whacked her out of fright as soon as I saw her. In that split second, I realised exactly what I had done and - I am not making this up - I leapt forward from my couch and tipped my upright Xbox 360 onto its side with an outstretched toe. The game crashed. The disc miraculously survived. My mistake was not saved. Maybe I haven't gone back because I'm kind of ashamed of that savegame.

I used to tell people that I was putting off going back to Dark Souls because to know it completely would make me sad. I like living in a world where some of the best parts of Dark Souls lie ahead of me. Then again, there are mysteries in this game so deep that even those who have finished it countless times and received an elusive Achievement ostensibly rewarded for doing absolutely everything still cannot solve them.

I think the real reason I've put it off is simpler: I'm sentimental about games like Dark Souls. You know when you play something so good that you feel depressed when you finish it? Often that's because there won't be another one along for a while. In Dark Souls' case, we may never see its like again. A bit like Portal, which also featured in this series, the internal mechanisms of Dark Souls have clockwork economy and precision; it is difficult to imagine how they can be improved or expanded upon.

The soul still burns Rich Stanton pretty much embedded himself in Dark Souls, writing about it for Eurogamer several times. His Telling Tales: Skyrim and Dark Souls article explores how two of 2011's best RPGs take drastically different approaches to storytelling, although Becoming the Dark Soul is my favourite piece of his, relating his experience unlocking the game's most difficult reward and talking about what it came to symbolise.

The first time I understood absolute geographical relativity of everything in Dark Souls' contorted, non-linear environments was a special moment. So was this guy.

With Portal, a lot of that had to do with the story being so elegant and complete. In Dark Souls' case, however, it's because it was designed in a way that has become unusual - full of indirect storytelling, unsolvable mysteries, tremendous challenge and the expectation of repeated play. These things are disappearing from our games, like so many souls lost on a bridge somewhere by a hollowed man who can't make it back to collect them.

It is well accepted that Dark Souls is a game full of dead things, including you. From top to bottom, anyone who is still pumping blood is generally doing it on time borrowed from some greater evil, sorrowfully throwing themselves on your swords, axes and fireballs as much to end themselves as to halt your progress. Even the NPCs, when they see you, show little excitement. "Oh," they may say. Most of them don't even move. There is no life.

Rich Stanton called Dark Souls "a game where the mechanics are also the metaphors". Maybe the reason the atmosphere is so mournful is that the entire game is a metaphor, full of ideas and systems that are dying even faster than the demons we slay, resurrected here not in hope of re-establishing them, but to ponder their moving remains.

If that is the case, though, then I hope it is the only thing Dark Souls gets wrong.