This is pretty much an extended side joke that happens on Family Guy. Imagine Peter Griffin said something about how bad it is to live in the old west, well thats what they keep pushing over and over again and it would be funny if it said it once and moved on to show all the different ways people are dying while tied together with a plot, but it's not, every time someone dies it's like "see the old west is really bad". If you;'ve seen the trailer you've seen the best stuff... well there is a bar fight which is pretty awesome and probably one of the best bar fights you'll see on screen in recent years, but it's supposed to be a comedy but it gets so far up it's own ass it forgets to be funny.
Got some good moments in it but personally unless your an avid cinema goer who feels the need to go once or twice a week during summer, i'd wait for this to be randomly on TV and then go... "oh that films on" and then watch it.
I would have given it 1 start but it deserved another for the bar fight as they went all out with it and had some good comedy moments in it.