I am not quite sure about that, although I wish the in-game fight was canon, because Drallig owns Vader a few times in that battle IIRC.
Cin Drallig does pretty good in that fight, but I think the brief scene in the movies is canon. Maybe both the game and movie fight are canon. Maybe they are a blend of the two. And Obi-Wan only sees the last few seconds of the battle. I don't know, maybe that's just me being hopeful.