Wasn't it last week the Unreal Engine that held the 360 back?
That was a month ago I believe but that was more about holding it back from competing with PS3 exclusives such as KZ2 and U2. The simple fact is that UE3 is still a good engine but it isn't optimised to get the most from the 360. At the end of the day though ME2 isn't a game that relies upon graphics to be the best in the business, people would rather they spent more time honing the story, gameplay and extra content instead. Don't brand all 360 fans with Selnors opinion that ME2 is the best looking game on consoles.