We've got two TV's and two Xbox's in our living room, and my wife has a gaming group. Match made in heaven, right?
So, what's a few solid games that ~8 people can play across two consoles/TV's? Racing, puzzle, whatever you've got...
If you like sports, I'd say sports games are pretty good for this. NHL, FIFA etc. are all a lot of fun, depending on what sports you like.
I'd assume playing a 4 vs 4 would be possible in most of them, but I'm not sure as I don't own any consoles, so you might want to make sure before buying.