The appeal is that they are fun.
I think that people have lost touch with what the whole point of games are: To have fun. Deepness and immersive-ness is not the measure of a game. Don't get me wrong, I like big AAA titles like GTA and Assassins Creed, but I can also appreciate Angry Birds and Bejeweled Blitz because they are a lot of fun.
Final thought: I think that Playstation Now could be an indication of where 'mobile' gaming could be heading, or rather how mobile and traditional gaming are going to collide. You could have the Playstation Now app on your iPhone, you sync a small controller with blue-tooth, and bam there you are on the bus instantly playing Assassins Creed 3.
Platinums: Red Dead Redemption, Killzone 2, LittleBigPlanet, Terminator Salvation, Uncharted 1, inFamous Second Son, Rocket League
