Darkness-Induced Audience Apathy: Grey killed his boss just before the game starts and kills a young girl during the game proper, making his fate well deserved. Due to the game's Nintendo Hard nature, it's unlikely you'll find many players who like it beyond the atmosphere.
Unintentionally Unsympathetic: Grey. What little personality Grey is given shows him to be a Jerkass, with him drilling a young girl to death during all difficulties, and it's shown in his backstory after beating the game on Hardcore mode that he crippled a co-worker, murdered his boss, and the game starts with Grey washing his hands in the bathroom sink to wash his boss's blood off.
The Manga (and Anime)
"Weird Al" Effect: The whole "fight and kill others like yourself in one off 'missions' to earn points to advance ranks and get fancier weapons" seems like some sort of commentary on online first person shooters (and Grey is just as much of a jerk as a lot of FPS players). Thing is, the story dates from the mid Eighties; Wolfenstein wasn't even 3D yet.