"It's become a stagnant genre, and it's time we had an Doom/Duke Nukem/Unreal/Half-Life successor"
The reality is many games single player aspect back then don't hold up very well if you play them back to back with modern games if you measure them on a feelings and "this is so awesome" standpoint, the rise of the cinemtic game - even as me an older gamer has shifted my preference hierarchy to want "both". I force myself to play brutal doom to get my "gameplay vegetables" because I hate the fact that hollywood props and cheap tricks give human brains higher highs in terms of excitement over intrinsic gameplay in terms of single player experiences. I really hate the fact that when I go back and play doom 2 I wish it was some hybrid of the cartoony doom I know and love and the best elements of hollywood deadspace, but minus the hollywood hyper realism. I was never a fan of the push towards realism in doom 3 on mars, I always loved the pixel art/toony type style of doom 2 and it was kind of awkward seeing the Cyber-Demon rendered realistically, when doom 2 had more of an artistic comic vibe with it's enemies like the walking spider brain that felt poached from Teenage mutant ninja turtles.
To say that modern games are all boring is a bit of an overstatement, they certainly DO cause excitement in their hollywood parts. I enjoy Assassins creeds world even if I have serious issues with the dumbed down combat when compared to prince of persia series also made by Ubisoft. I really do think the push for hollywood has seriously made developers dumber, newer generations of developers raised on Halo regen shields and hollywood handholding campaigns has been infecting all of gaming, I seriously question developers, that "they know what they are doing". Too often even simple and cheap to program things are missing in many modern games.
The problem modern games main problem is gameplay, PC (modding/dedicated servers) and challenge related but this is publishers trying to drive DRM and control the market by confiscating game ownership with encrypted steam games via steamworks DRM for multiplayer/matchmaking. Shooters FPS/TPS, they are most certainly by the numbers but the mass gaming audience prefers hollywood action movie over intrinsic gameplay generated by fun and challenge. To be honest with you, I thought half-life 2 was just a giant pile of fail, trying too hard to be the hollywood action movie type game it never really was really "here's an empty base with an experiment gone wrong, you are on your own". Half life one did it's best to get out of the players way, while Half-life 2 feels like a very force sequel. I think it comes down to Valve not really not know what they are doing storywise. When I got to the buggy desert/section I gave up, I just got too bored. Half-life 2 was poorly made in many areas and poorly paced. I lost interest.
Half-life, while it was one of the first 'movie based games' where there was story integrated into it, but it wasn't done as obnoxiously and overbearingly as it is done today. That being said, some obnoxious overbearingness works, if you play the singleplayer campaign of Transformers - Fall of cybertron, you'd be hard pressed to say that it couldn't compare in terms of fun to Doom 2.
Doom was made at a time before the integration of 'hollywood action movie/cartoon show inside a videogame' was mastered. The newer generation has problems going back and playing games that haven't mastered the hollywood integration like Mass effect 2, Call of duty and transformers fall of cybetron (sp campaign). I don't fault newer genreation gamers for that because even I as an older gamer know that when CPU/GPU power hit a threshold it was just easier to use high def AV to flash our primate brain in sensation, problem is instrinsic feelings related internally generated gameplay are easily overwhelmed and outcompeted in many (not all) instances of set piece hollywood bullshit. The kind of excitement we get from the hollywood is of a different character them the stress based excitement from challenge and mastery.
This is why while we might have all enjoyed mass effect 2, it left us with a kind of shitty aftertaste like we lost something, and we did. Since hollywood stimulation and gameplay stimulation seem to compete and often times are at odds with one another in our brains where one drowns out the other, more of then not, gameplay losing out because it causes stress and costs the brain energy and passive audio/visuals goes down easy.