Not even the analysts predicted the RDR effect so the first week is understandably way off. It will still hit a million this year and the 2m I was expecting LT. I personally feel the reviews were skewed by expectatons built up during the long dev time, pc owners disappointment and the usual anti-M$ bias. They won't stop many 360 owners from giving it a try.
Will we be trashing every PSWii exclusive that doesn't sell 500k first week by resurrecting their old threads? It's only fair. Or equally unfair.
Perhaps they are not the same people but some fans will trash Reach for not deserving it's sales while others use relatively low sales for ME2 and AW as 'proof' of lack of quality and confirmation of their favourite console's superior library. All's fair in the console war.