Vietnam Still Means Bad Games
Vietnam has managed to be a war without a game that was remotely entertaining attached to it. There have been several epic failures, but the games have been crap. And it's not like, say, the Civil War where the weaponry used doesn't correlate to a good game. Heck, if you took the Far Cry engine and made a Vietnam game based on that, you'd probably have something worth playing.
The developers of Shellshock 2, well, DIDN'T do that. They made the usual shit Vietnam game that has rejected by the public repeatedly in the past (not coincidentally, this one also bombed). The visuals are absolutely abysmal. The audio is equally abysmal. The framerate is abysmal. The level design is abysmal.
You're, of course, in Vietnam having to the fight the n. Vietnamese AND infected troops who are like zombies, but a mere fraction as cool.
The weapons are obnoxious. Headshots are occasionally recorded as headshots. Some enemies take multiple headshots (bizarre for normal human enemies). Grenades barely go forward when thrown. Melee weapons are so weak as to be borderline useless.
There is literally no reason to ever play this game. One of the worst ones out there.