Stop thinking this is real and literal and understand this is a game meant to make money.
That being said...
There is Canon, We have seen it in Darkspawn Cronicles in Alistairs choices, in Awakening if you import a Orlesian Warden, and in Dragon Age 2 there will be a default canon if you dont import your save data.
The canon is a Grey Warden neutral path as I have explained, its whats best vrs the blight. Not whats right or wroung.
Thief-of-Hearts wrote...
There are bits of cannon regardless of playthroughes. At the end of the game these things always happen:
Calian is dead.
Duncan is MIA.
Lothering is destroyed.
There is a new Dwarven King.
Sacred Ashes are found.
Eamon is saved.
There are no longer werewolves.
Blight has ended.
Corrections and Addedums
Duncan Recruits a New Warden(All the other Origens characters are in game actualy)
Calian dies at Ostagar.
Duncan is presumed dead. (You never actualy see him die or find his body)
Lothering is destroyed.
Templars end up killing the mages, or Mages are saved.
Dahlish survive and Werewolves are Killed or Cured, or Werewolves survive, Dahlish are killed or turned into Werewolves.
Anvil is redicovered or destroyed, a new king is on teh dwarvern throne, Bhelen or Harrowmont.
Connor and Isolde are saved, or Connor is Killed,or Isolde is Killed,or Bargains with Desire demon are made or demon is killed.
Sacred Ashes are Found, Cult is destroyed or left alone, or Sacred ashes are found and location is never revealed.
Not a real variance in DLC but we have confirmation they are tracking wether you did it or not.
Landsmeet (Too many varibles)
Confirmed Canon, Alistair kills Lohgaine and assumes the throne. I belive its a confirmed "Hardened" Alistair.
Confirmed Canon, Dark Ritual with Morrigan, The Warden if male or Alistair if female.
Thats the basic rough rundown.
What shows up in more then one instance is Werewolves, and Golems. We have to extrapolate what events are likly to have occured. I like to think Anvil+Bhelen as thats the most beneficial to teh dwarves and the wardens cause, On the Dahlish side till talking to lady of teh forest then betray Zathrian once the warden learned the truth. Warden may be racist against elves, but still the werewolves were the superior army compared to the dahlish(Since the dahlish were not ALL dahlish just the clan taht was there while the werewolves were hunting everything in the forest elves, humans, dwarves whatever and infecting them to boost their ranks.) If on PC I suggest getting the mod "Wolf Shop" so that you get a werewolf vendor to replace varehil.
The events of the circle tower.....well they have to be a course that you get Wynn in, generaly we have to assume the mages were saved because of this, but as said you could have teh scenario where wynn is still there but the mages got screwed. So this is up in the air but it still has got to be a way Wynn is recruited.
Also along these same lines, the Sacred Ashes can NOT be defiled.