I could only afford one console, so I had to go with the one that had the most games I liked. Now there are dozens of Wii and WiiWare games I don't have the time or money for, so I definitely don't have the time or money for a second console right now. With stuff like the XBox Live indie games and 3D Dot Game Heroes, both consoles finally have some stuff that can make me a little jealous, but not enough to make a 2nd console a tastier deal than 5-20 more games.
EDIT: I didn't even buy a console last generation, and I probably would've eventually purchased a used DreamCast or a PS2 if it wasn't for Wii Sports and the Wii remote. That changed everything for me.