Funny you should say that considering PSO has the most shallow gameplay of the ones I mentioned.
That's a debatable statement (especially considering PSO is the oldest of the ones you mentioned), but my point is that you're relying on the exterior stimulus of live interaction to fortify a game that is, by itself, pretty boring. If you admit that the game is boring but you only play it because you like chatting with friends... why not just pop into an IRC chat or go outside and play tag or something?
I'm not arguing against the idea of multiplayer games and certainly not against their potential, particularly online, but I would say that, if it's not something you'd play on your own as well as with friends - ie, if it's a repetitive, simple, shallow action game, as most multiplayer games currently are - it's not good enough, at least not anymore.