A great way to experience the Mass Effect trilogy on 7th generation hardware, but definitely more compelling of a purchase for PS3 owners. It's just a collection of the base games if you're on Xbox 360. If you're on PS3, you get a lot of extra DLC included on the discs. The PS3 version includes:

Mass Effect: Bring Down the Sky
Mass Effect 2: Cerberus Network (new copies only, but free on PSN)
Mass Effect 2: Kasumi - Stolen Memory
Mass Effect 2: Lair of the Shadow Broker
Mass Effect 2: Overlord
Mass Effect 3: Online Pass (ME3 Multiplayer is defunct)