In a few days (Aug. 11th to be exact), 360 owners will be able to use the upcoming update to play Games on Demand among other features. The games that will be available were just announced. Those games are:

• Assassin’s Creed
• Burnout Paradise
• Call of Duty 2
• Elder Scrolls IV: Oblivion
• Fight Night Round 3
• Kameo: Elements of Power
• LEGO Star Wars: The Complete Saga
• Mass Effect
• Meet The Robinsons
• MX vs. ATV Untamed
• Need for Speed Carbon
• Need for Speed: Most Wanted
• Perfect Dark Zero
• Prey
• Rockstar Games Presents Table Tennis
• Sega Rally
• TEST DRIVE: UNLIMITED
• Tom Clancy’s Rainbow Six Vegas
• Tomb Raider Legend
• Viva Piñata
• Viva Piñata 2: Trouble in Paradise

No word yet on pricing but usually digital copies of games are roughly the same price as in-store.

[ Source ]