I just bought a Nintendo Wii and attached it with the included component RGB cables to the aux video inputs on the front of the receiver and I'm not getting any audio or video from the Wii.
IIRC, the aux video inputs on the front of most receivers I've encountered are red, white and yellow jacks.
If that's the case for your receiver, then they are not expecting composite video signal. They are looking for stereo audio (red/white jacks) and a composite video (yellow jack) signals. Try either going thru the back of the receiver (along with some kinda audio feed*) or if you're really, really intent on using the front aux inputs for this application, then you're gonna have to use a red/white/yellow audio/video combo cable between the game and the aux port. ...attached to the proper outputs on the game, of course.
If these aux video inputs on the front of the receiver are in fact red, green and blue, then I'm outta ideas.
* (Component video doesn't pass audio - never did, never will)