A couple demos was released on the Xbox Live Marketplace today; Aliens vs. Predator and Dynasty Warriors Strikeforce. Both are currently only available to Xbox Live Gold members. Silver members come back in a week or so.

I am tempted to try out Aliens vs. Predator, but I really doubt I would have time to play it between mission of ME2. And as for Dynasty Warriors. Maybe if you make an Aliens vs. Predator version of DW I would start to care.