If you had to show somebody what is great about gaming with only 5 games...

[Quickdraw McGraw]

Yakuzaice said:

Super Mario Bros. 3 + Super Mario Galaxy (since Flower is short I'm going to cheat and add galaxy)
StarCraft
Flower
Half-Life 2
Shadow of the Colossus

This is a brilliant list.
I'd switch StarCraft and Flower, assuming they have to play the games in the order listed, but otherwise, this list would likely be mine as well.