Facebook games are getting better at the "game" things I guess, but their is still work to do on that. The social aspect is more than often a lure. It has worked pretty well, but it really gets old after a bit. They are good browser based games with good social aspect though, but none that have to thank fb for that.
For Google/Apple's games, they work because they open "video games" to a broader audience. but games you can pick up and put down in a minute aren't what a gamer will look for. Gamers won't disappear just because of casual game on phone. It's just not the same usage.
Wii/Xbox/PS3 have specificities, and it's up to the game designers to figure what support is suited for what kind of game. I really don't enjoy action games on a phone, the command are crappy and most of the time they hide the screen (you know, because of the tactile thing) and I sure won't buy scrabble for my Xbox. As for the networking aspect, things are going in the right direction I think.
PC has the most wide panel of possibilities from controllers to social things and Internet connection, so it gives it an edge. But my guess is no platform is going to disappear, they'll just radicalize.