Here's a party game - take a game where you can, like, just play it right now. Like quake live or counter strike or such. Now imagine you had to go through 80 levels first, before you could actually play like that. What would it add? What would it do to those game? Would it make the 'end game' seem somehow more interesting for all the effort you put into it? Perhaps it would? Would it have been increased in interest enough to warrant the time spent before you could actually play the game.
It's a party game - call out a game and then 'end game'-ify it!
PAC MAN! End gamed! How would that end up looking? Then at level 80, you can play...regular pac man! But now it's epic cause of all the levels! Surely if you spend hundreds of hours on something, it has to be epic!