I think the biggest fun factor that the CONSOLE has to offer is the fact that allows you to have FUN in the shortest amount of time. You take the console out of the box, plug in the controllers and power, connect to the tv and you're all set. In less than 30 minutes from the time you opened the box, you're already jamming on the controller having a helluva time.
On the other hand, for the PC, before you can even play a single game, you'd have to set up the PC first. Install the OS. Configure odds and ends. Then you'd have to install the game. Sometimes, you'd have to connect to the WEB to download the latest patch for the game. Then and only then can you start to have fun. Also, you'd have to have LAN connection be able to play against other players. A lot of work... Pero, for me, part of the fun is actually doing the chores mentioned above. It's also fun to be able to tweak your system to your hearts content to squeeze out the last ounce of horse power and framerate for that new game (DOOOOOM3!!!!)
Plus there's the potential to extend the lifespan of a PC game via player community MODS and enhancements.