I think the reason why a lot of us feel a little offended (or put some other negative reaction here) is that those reviews can decide whether a person would want to play or not. It's only natural for someone who loves SOMETHING would want to spread the word, to find more people who also have the same similarities. What I found troubling about those reviews is that they gave a review based on how far away fallout 3 was from fallout 1 and 2... which to me doesn't really accrue the quality of the game or not
Come on now - we're talking about two reviews that are posted on the NMA forums. It's not like we're discussing something by a professional as an "official" review on something like the Escapist or IGN, here. And considering that NMA is a site dedicated to the Fallout games, long before Bethesda had even considered doing anything with the series (meaning that the primary demographic is naturally going to consist of fans of the first two games, obviously,) I don't think it'd be terribly off-base for any of the reviews to be found there to reference those games in their reviews.
This really isn't very much different than if I were to come on this forum and post my own Fallout 3 review - and if someone were to base the decision of whether or not to buy a game based solely on one review by just another geek (and not one by someone who actually does that sort of thing for a living,) then not only is there not very much you can do; but chances are they're already have going to have made up their mind well before now, and likely aren't going to have ventured onto NMA by that point.
In short, let's not make a mountain out of a molehill, here. Any game you happen to be a fan of, there's going to be plenty of people who have the opposite reaction; and they get to throw their opinion into the ethers just as much as anyone else does. (And let's not forget we're talking about reviews on a site that's generally known as having wanted a more "traditional" take on the franchise, which you're probably going to realize by the time you've been there long enough to bother reading their members' reviews on the game.) And it's certainly not like Bethesda is hurting so bad for sales that they're going to miss the (debatable) losses they're taking because one or two people decided not to buy a game based solely on a non-proffesional review on a fansite that caters to a very specific demographic...
EDIT- And don't get me wrong, I'm not saying I particularly agree with the tone of a lot of the reviews that get put on NMA. There's a trend in videogaming that I'm not overly fond of - and it's this rather annoying sense of entitlement that seems to overcome a number of dissapointed gamers (and this is no way limited solely to Fallout, by any means,) and that first review in particular seems highly colored by that offended sense of bitterness. But at the same time, it's just a bunch of guys saying what's on their minds; and there's never going to be any shortage of that on the internet.