I always buy a console for a particular game or games. There's no reason to buy it until games you like are out for it. Usually it's more than one game though. For me it was:

Playstation 2 - Final Fantasy X, all the old PS1 games since I never had PS1
Wii - Twilight Princess, all the old Gamecube games since I never had a Gamecube
Playstation 3 - Final Fantasy XIII, MGS4
DS - don't remember, I played so many great DS games
3DS - Kingdom Hearts 3D

Hey my list is pretty similar to WK's!