Dragonfly2012: I also think that they should have sticked with better multiplayer engines. I mean Quake 4, Doom 3 and Rage were more or less single player games at their core. If you look at what games made id successful, multiplayer was a huge part of that. Doom 1 was the first game I played online (by modem). Quake 1 with it's Quake World extension really got many people into playing online on the Internet. And 32 player support was a huge thing. Even today a lot of the games don't support that many players.
I don't know what made them think that multiplayer isn't important anymore. If you look at some of the best selling FPS like COD and BF, loads of people never touch the single player campaign and jump straight online.
Of all the Quake games, Quake 3 Arena was the one I never want to see again. I loved the single player environments, limited that they may be, in the Quake and Doom worlds. I don't mind the MP as an addon, but when the game is built as a multiplayer game, and then they throw in a lousy single player experience to "appease" people like me that don't want to share their toys.