I was born in 1980, played Lode Runner on a Macintosh when I was three/four years old, had an Atari 2600, owned a NES in 1985/86, had an Amiga 500, then SNES in 1991, a 486 PC soon after. You can see why I'm brainwashed into thinking that classic games were simply better.
I started to lose interest around the same time as the original poster, early 2000's. The last games I remember playing the living crap out of were Baldur's Gate II and Roller Coaster Tycoon 2, oh, and Diablo 2.
Things that bothered me the most:
-The shift to 3D only games. Remember Symphony of the Night? I remember magazine critics complaining that it wasn't 3D, and yet it stands out as one of the best games from the late 90's, despite is lack of "innovation."
-Nintendo in the N64 era losing most of its best third party developers because of their refusal to use the CD format. Nintendo was King to me since I was five, and it was hard to accept that the N64 wouldn't have all the best Capcom, Konami (other than the 3D Castlevanias), and Sqaure games.
-The PC in the early 2000's was still riding a wave of generic RTS Warcraft/C&C clones. And also the focus of most of the best companies shifted to online only multiplayer/no single player games. I never thought of video games as social media. For many, this is when their interest in gaming began, but I wasn't interested. I especially found pointless the FPS games where all you do is shoot at other user controlled players and then everyone immediately respawns after dying.
-And finally, the generic We Wish We Made Hollywood Movies syndrome. I know that most game developers are nerds, and love fantasy/sci-fi movies as well. But I always kept these separate in my mind. I hate seeing hammy or wooden acting from 3D rendered, not human enough faces, spouting cheesy lines when all I really want to do is play the damn game.
Take all the above with a grain of salt. These are simply my experiences and opinions, and I'm sure that there are good games being made today and many exceptions to what I'm talking about. Hey, Cave Story was awesome. ;)