All the arguing about which ending is starting to grate on me. Each player can have there own ending, based on their Shepard. Especially when you consider the Paragon/Renegade paths. Control let's Shepard be the Big Hero for Eternity, Destroy combines revenge and the sacrifice of others so that Shepard may live. Synthesis is presented as the ultimate third way. It's the hardest to get EMS-wise, and is presented by the Catalyst as the ultimate evolution of man. Refuse is also a great ending, even though it's mostly a reverse fanservice.
As for a canon ending, it doesn't matter unless there's another game, but if the story is to be continued, then these wildly different endings must be combined somehow.