The thing is, narrative in gaming is absolute shitwank, it's atrocious, for the dogs, etc. Besides Spec Ops, which is an extremely divisive game due to how actually complex and intricate it is, let's count the actually really good, deep and interesting stories in games, shall we?

Silent Hill 2.

Oh, that was a short list, wasn't it? This is a medium where poorly written tripe like the Last of Us, Mass Effect, Final Fantasy games and Bioshock get's hailed as the "Citizen Kane" of videogaming. The entire bit of narrative in games is an absolute shitfest, where the most popular discussions about video game plots are about who likes shagging who, and who would win in a fight against who. That's on the level that most who actually give a toss about narratives in games come from.

Also, have you actually read Heart of Darkness? I haven't met anyone who's actually read it and claimed ripoff, the stories are really not similar in a tick, there's similarities sure, but most of it is just an homage, the actual plotline and themes presented are widely different.

Also, most of your complaints are just, dare I say so, silly. Gunplay and writing are subjective, so I can't really argue with that, but are you seriously complaining about lack of sidequests? Of course the games thrives on its narrative, it's a narrative based game. I don't slight Portal for having too small a plot, I don't shun Starcraft because it had too few railshooter segements, why are you complaining about Spec Ops having stuff that doesn't belong in it? It's a 6 hour long very focused shooter, not a fucking RPG, what would Spec Ops gain from unnecessary padding?