Right first of all I understand there is no true canon in Mass Effect.
However when starting a new game in Mass Effect 2 there is a default story that exists which includes all the big gameplay decisions, and even resolutions to certain assignments.
I would like help to chronicle this 'canon' somewhere on the website and so I am starting this blog to gather everything that can be summarised. I'll put as much in as I can but feel free to jump in.
Firstly the big decisions: The Council is dead, sacrificed so that the Alliance fleet could attack Sovereign. As a result humanity has taken control of Galactic politics. There is no default love interest, however a male Shepard has let Ashley live, and a female Shepard has saved Kaidan. However Wrex was killed on Virmire, allowing Wreav to take control of Clan Urdnot. Also it seems that at least some of the Cerberus assignments have occurred, simply because there is reference made with Jacob to Shepard's history with Cerberus. Also Nassana Dantius doesn't recognise that you helped her with her sister.
I'll add some more after I play the game for a bit. Also could any moderators give an opinion about whether this information should be included in any official articles?