OP your argument collapses under scrutiny because it's predicated on the premise that A) all criticisms hold equal weight/value, and B) that actual non-nonsense criticisms aren't rooted in an element of inherent subjectivity.
To A) you need to consider that game criticisms, especially on the internet, are far less criticism and more sweeping, unjustified judgements. E.g. if someone spouts off that GTAIV is a "bad game", that's not a criticism. It offers no qualification at all. So a retort saying "but the game sold X tens of millions", is a legitimate argument because the former unqualified judgement is shown its inherent invalidity due to the fact that the person rendering such a judgement is in the extreme minority; i.e. millions of gamers don't come out in droves to buy bad games---they can and do so for flawed games, but never for irredeemably bad games.
Which brings me to point B), when your typical internet gamer renders an "criticism" that a game or facet thereof is "bad", they are neglecting any understanding that their own judgement is rooted in inherent subjectivity. Every gamer has their own subjective biases and prejudices when it comes to games. Some might say turn-based combat in RPGs is bad and makes for bad games. That's not an objective assessment. So not all criticism is valid and some can very well be dismissed for the fact that the person criticising said game or facet thereof is inherently biased against said game/feature and so their criticisms have far less value.
REAL, legitimate and properly qualified gaming criticisms surrounding the less subjective aspects of games are the valuable things that most gamers will be less inclined to challenge. And frankly I've been posting on forums forever and I can't think of one single instance of a person trying to rebut a legitimate criticism of a game with "b-but it sells well". In which case, I'm really curious what spawned you to make a thread about this?