If the stuff you are playing on is just an added layer to the experience and not the experience itself then it is not a video game, it is a game.
Wii Sports would be pointless without the Wii or the game because waving a remote around doesn't make it a game on its own.
On the other hand Singstar, DDR or even Eye of Judgment can be played without the device and thus are not video games but games (eye of judgment is mainly a card game and can be played without the ps3).
Wii Fit in the majority of its activities can be done without the Wii. There are a few in it that are gams and need the Wii to have a point just as the sports in Wii sports do.
It's not a question of simplicity or ease of play but what a video game is versus what a game is that uses a video game machine for a song track or a visual representation or a score alone and doesn't have the software as the essential experience in the activity.
When it comes to casual and non casual games beyond the question of what is a video game then the purpose of the video game comes in. Games that are casual and core are ones that can appeal to both people who are trying to master the game and to those that will just play it to mess around (Guitar Hero and to a lesser extent gta and mario are kind of like that and appeal to both audiences).
Thanks to Blacksaber for the sig!
