Half Life was never good.
As bad as COD, Halo, Goldeneye, Quake 2 and other popamole garbage.
Serious question - what's the fundamental difference between Half-Life and Duke 3D? I'm not trying to claim they aren't notably different, because they clearly are in goals, gameplay and design, but what is it that makes Half-Life popamole while Duke presumably isn't?
As Lyric Suite said earlier, Duke 3D represented part of a wider push towards "realism", which I take to mean setting the game in semi-believable locations and placing enemies in semi-logical locations. The only big differences in Half-Life are that there's less combat because the game often switches to platforming or puzzles (also a feature in Duke, but less pronounced), and the game has more movie-like elements (getting knocked out and thrown in the trash compactor of doom, occasional brief sequences where people talk to you to tell you plot details, and so on), while Duke conveyed those mostly through text between levels and very, very brief setpieces ("WE'RE GONNA FRY YOUR ASS, NUKEM!").
Similarly, what are the key differences between Quake 2 and Duke 3D? I agree Quake 2 sucks shit, but that's down to unappealing visuals, clunky and boring combat, and occasionally awful bits of level design.
I can't help but wonder if Half-Life had come out a year and a half earlier on the Build engine and been more or less the exact same game, only with like 5% more enemies and NPCs speaking to you in text rather than voiced dialogue (as in Duke 3D or NAM or whatever), the same people who shit on it would be praising it as a high point of the FPS genre and the best of the Build games.