There was a time (just typing that makes me feel old, but anyway) when gaming was a very solo experience. Single player was the main game mode, and often the only one. Multiplayer was you and your friend(s) hanging out in the arcade, trading off, beating each other up, or beating hordes of foes away. Then when gaming came to the home, it was sitting on a couch by your self playing Mario .
As consoles evolved (to the Xbox) the shooter started to rise, with you and up to 3 friends wandering around shooting each other on sight. Through all this, games still had a strong single player mode, with multiplayer just something to do with friends. That all changed with the current console gen. Now, I realize the Xbox and the PS2 had online multiplayer, but nowhere near the level of the 360 or the PS3. And PC, but that's another story.
Now the best selling games, might as well not even have single player *cough cough COD*. The single player experience has taken a back seat, everything needs to have multiplayer! What happened to the days of getting the full game, with out needing to play with other people?
Unfortunately that doesn't seem to be about to change. Most of the big games announced are multiplayer exclusive or multiplayer focused. A quick look at http://www.gameinformer.com/b/features/archive/2013/06/19/the-next-generation-confirmed-list-of-games.aspx list shows the about half have some kind of multiplayer. The solo gamers is a dying breed.