Oculus Rift is a virtual reality headset to help enhance a gaming experience.

Ouya is an android-based console platform aimed to provided a low-cost console with an interesting developer business model that current consoles don't provide. I would also say it has a chance of being a popular option in the 'media brick' market (Apple TV, Roku, Boxee, etc.) as well.

They're two completely different things, the only common attribute is wanting to provide a "different" gaming experience.

However both the success of the Ouya and even the Oculus Rift will depend greatly on the developers supporting it.