I don't think major gaming sites have been trustworthy for ten years or more. It's all a sham, if I'm honest, and having worked myself in the industry, I have a bit more insight into how it works.
It's not NECESSARILY that the reviewers are bought or anything, it's more of the corporate mentality within big gaming sites (and many amateurs too), the lack of journalistic experience/expertise and the whole gaming aspect of it, it just makes for complete turds flying left and right out of their mouths.
SOME gaming journalists are good though, but they very very rarely go beyond the whole "ok, here's my own personal opinion on this game so take it as that". Most game reviewers are too drunk/dumb/restricted to have a personal opinion on anything, so they just go with the corporate opinion of whatever place they work in.
There have been plenty of scandals pertaining to this over the years. But the problem isn't restricted to gaming. Movie reviews are the same exact thing, although maybe a bit less chaotic and offensive to my intelligence.
Again, it's not that they are bad people without scrupulous or morals, it's just the nature of the game (ahem) and the way things work. Most of us (us who don't trust major gaming sites) would end up doing and writing much of the same crap they do, were we to be in their position. It takes guts, originality, thought, love and luck to be a proper gaming journalist doing proper gaming journalism.
:EDIT:
And I'm not even touching on the problem of how mainstream gamers take reviews, and how their opinions are influenced by reviews.
That's a very simple issue though: take Company of Heroes, for example.
For most people to buy that game based on a review, it'd have to read something like "This game is good because the story is inspiring and the graphics are great". Well, that says pretty much nothing about why anyone would want to play that game. What would say, however, would be something like "this game is bad because it's too focused on combat micro-strategy and tactics, and less on building a base and the traditional elements of a strategy game".
I'm not sure I'm being clear... Essentially, for me, and I do believe for most educated gamers, it's more important to know what someone didn't like about a game than what they did like. Someone tells me not to play Europa Universalis because it's too slow and too complex to get into? I'm gonna play it! I have played it to death, actually. Someone tells me not to play Call of Duty Somethin's because it's the same as all the others and the plot is even worse? I'm not gonna play it!
Now if someone tells me Europa Universalis is awesome because there's endless possibilities on how you build your nation, I might be interested, sure, but the same could be said about Rome Total War 2 (even though it would be less true). Someone tells me Call of Duty is awesome because it's epic and the plot is engaging, sure, I like those traits, but the same can be said about many other games.