I think that the main problem with a game based on the War in Vietnam is that most handling of the subject tends toward unrealistic extremes (like a lot of war games, come to think of it). Either all of the American soldiers are sociopathic crazies who slaughter enemies like its nothing while innocent Vietnamese try to fight them off, or the situations are reversed (usually with the Americans being draftees who oppose the war but can't bring themselves to dodge the draft). What a lot of treatments of the subject miss is that people on both sides of the war were human, capable of making mistakes and having more motivation than "gee, killing other people is fun" or "I don't know what I'm doing here."
And, if you want to bring up the My Lai massacre, yes, there were some insane U.S. soldiers who thought that killing innocent Vietnamese citizens was good fun. There were also soldiers in that same incident who tried to stop their fellow men from doing all that, and even went so far as to protect the innocent civilians from their comrades.
But, back to the game, I'm really hoping that someone at Treyarch (or whoever's doing it) puts a lot of work into the story, and doesn't make another derivative shooter.
