Videogame journalism has a great responsibility because they are essentially guiding their readership on which videogames are worth purchasing and which are not. This is real money we are talking about; money that a good majority of their readership doesn't have excessive amounts of. Videogames are not exactly cheap, and many people are using the little they have on them.
It is the responsibility of videogame journalists to convey to the reader as neutrally as possible the quality and details of a videogame, to help them make their purchase decisions. Artificially praising a game that does not deserve such praise, in order to entice people to buy the game, is ethically wrong. Doing so for personal gain from the game's developers or publisher is absolutely horrendous (and should be illegal, if it's not already.)
But that's exactly what has been happening for quite some time. Most of it is done under the wraps, making it even more condemnable and unjustifiable.
Several high profile journalists and reviewers who have more moral integrity and oppose this practice in principle, have come out to criticize it. There are several ways in which publishers (and sometimes even developers) may, essentially, bribe journalists to give positive reviews.
Some publishers may sponsor a videogame journal (which, especially if not publicly divulged, is at the very least bordering crossing the line.) Others invite reviewers and journalists to experience and play early versions of their games, and there is much subtle (and sometimes not so subtle) bribery going on here (such as travel expenses and stays at high-quality hotels paid by the publisher, and outright giving gifts to the journalists.)
Sometimes this can become really egregious. Sometimes publishers will outright "blackmail" videogame journals with their early access policies. In other words, they will give early access to their game only to those journalists who have given positive reviews of their games in the past, and will stop sending them to those who have given negative reviews. (Naturally an early access review copy will be accompanied with a strict contract forbidding the journalist from distributing the game further.) There have been actually cases, where journalists have had to sign contracts to make a positive review in exchange for an early access copy of the game, and the contract has a strong non-disclosure agreement clause (iow. the journalist is bound by the contract to not speak about the contract to anyone.)
Sometimes this kind of bribery can be more egregiously public. For example the Games Media Awards is a yearly ceremony where journalists are given awards. The awards are (or at least were for a long time) voted for by PR companies, and sponsored by publishers, not by eg. gamers or even the journalists themselves. (There may be some "gamer awards" and such, but those form only a few of the awards.) In 2012 it became really egregious when the publishers enticed the journalists participating in the ceremony into promoting certain videogames, with material goods being involved for those who did (including up to a PS3 console being given as a gift.)
There are many other examples of this I'm not going into (such as the so-called "Doritogate", also from 2012). My point is, videogame journalism has been rampant with extremely dubious practices, with game publishers, PR companies and sometimes even developers enticing journalists to give positive reviews and recommendations, using bribery and sometimes what effectively amounts to extortion.
To be fair, many such journals have upgraded their policy statements to rectify this, to change it to a more open policy where things like sponsorships and other forms of interaction between the journal and game publishers are more openly divulged. More and more videogame journals have been doing this.
It is probably no coincidence that this change has been happening relatively shortly after the gamergate movement started.
Gamergate is a consumer revolt against corruption in videogame journalism. Of course the movement has been heavily denigrated and defamed both by journalists and feminists, who have (quite successfully) painted it as nothing more than an aggressive sexist movement against women in the videogame industry. No doubt the corrupt journalists, those who unashamedly take bribes from publishers in secret, have welcomed this defamation of the gamergate movement, and added to it. They will, of course, just attribute the claims of corruption to "nothing but a conspiracy theory".
The Wikipedia article on gamergate is quite a disgrace in this regard. Its core problem is that Wikipedia's policy is to build articles based on sources, and those sources are the videogame journals and the journalists, because those are all the "official" publications. In other words, Wikipedia is effectively asking the journalists themselves whether there is any truth to the corruption allegations... Yes, because the most trustworthy source of information is the accused.
However, that's not all. Not only is Wikipedia relying almost solely on the word of the very people that are being accused of corruption, the article has clearly been written in a highly biased manner by feminists, or feminist-minded people, with an ideological agenda to discredit the movement. The article spends absolutely disproportionate amounts of space to go on and on and on about the "harassment" and "threats" and "sexism" that some individual people have experienced. Even the few mentions of the actual points of the movement are quickly dismissed and "debunked" with copious amounts of weasel word salad (gotten primarily from, you guessed it, the journalists who are being accused of corruption.) This is "poisoning the well" 101. There isn't even a shred of neutrality in the article.
Regardless of the extremely successful defamation campaign against the gamergate movement, some good has nevertheless arisen from it, such as those updated policy statements. (Whether they will have an actual effect is another thing to be seen, but at least in principle it's a good thing.)