The main thing for me has been a significant drop in a sense of 'community'... ironically as gaming has become more and more mainstream and more and more popular, the actual sense of a cohesive 'community' has died off. Whether it was regular servers and clan-scenes in the 1.3-1.6 Steam games, or CoD1/CoD2, or whether it was the fact that everyone at some point used things like Xfire for much more than just simple chatting... it feels like the PC gaming crowd has been dispersed over many titles and many platforms. Game design reflects this, too: less and less focus on teamwork and supporting clan/league scenes, more and more focus on lone-wolf play and heaping on the achievements. Most of all this is what has killed off all the 'giant' MMO games for me, WoW being the most instructive example: from server-based communities and guildscenes to a total solitary experience, even though the game is more popular and more widely played than ever. It's a shame.
I basically think it's because PC gaming came out of the hobbyist/enthusiast closet, moving from quite a specialist and quite nerdy (not to mention expensive) activity into a more mainstream pastime. 5-10 years ago every PC game had a real hardcore core of players that would sustain it, even if the game itself had faults or bugs; small things such as design imperfections barely even mattered! Nowadays we have highly-polished games that are graphically stunning, but every single time it fails to generate a 'buzz' in the social sense.
I know there's the whole LoL/DotA2 thing, with the whole tacked-on streaming phenomenon... but something about those communities and that 'style' of game just doesn't do it for me. It's not friendly, and the whole culture of watching YouTube videos and 2 hour long streams is completely alien to me. Everyone is lured into a sense of 'participating' in the 'scene', when really all they're doing is sat back being passive backbenchers. Bring back the banter of a Day of Defeat 1.3 server!
