Quality is not a relative term.  

I also happen to like most games that reviewers like, but that's a matter of preference, not quality. 

When someone says "Blizzard makes low quality games", or "Dead Space is a high quality game", they make a universal statement, not just telling how much they enjoyed the game. 

And while I'm aware that sales are also flawed at indicating true popularity, I believe that no game that is enjoyed by many should be called "low quality" by others.

Quality is a relative term.  That universal statement is in comparison to their and others ideas of quality.  Doesn't make it absolute.

If it is absolute as you claim can you list the criteria for Quality games or does it tend o vary from person to person?

@Alterego: Umm... What's the logic behind sales not being an indicator of games true popularity? I'm not saying it would be in every single case without exceptions, but it is the best indicator we have for popularity.

@nitecrawler: Quality is universal term. It does, however, have certain variation between individuals.

if it varies between individuals it is subjective.

definition of subjective: relating to properties or specific conditions of the mind as distinguished from general or universal experience.

definition of universal:applicable everywhere or in all cases; general: a universal cure.

can it be universal if it varied between individual experience....? I think not as that makes it subjective.

@nitecrawler: It is universal and it can mean only one thing. The biggest variation comes from people focusing on different aspects on a product.

Quality doesn't equal preferration. However, it's much more easier for people to prefer quality product than a bad quality product. There are some games that i can say they are good in quality but i just don't like them (like Halo) and some games that definately aren't good in quality, but i like them (like Excite Truck).

To put the term "quality" to another words, it would be something along the lines of "how thought out" or "how much effort put".

I agree with that, it is the best what we can have. 

But still, popularity would mean the actual amount of people who are enjoying a game, while sales might be somehow increased with hype, massive advertisement, branding, metacritic bribing, etc. It is still related to popularity of course, when a game sells significantly below or above expectations, but we can't clearly state that for example LittleBigPlanet is more popular than Wii Music, or that Modern Warfare 2 is more popular than the previous Modern Warfare game. 

@Alterego: Yes. I agree with that. I usually like to look how popular (or how the game delivered) a game was by looking how its sequel does. Legs are another thing to watch.

Btw, your new avatar reminds me a little of JaggedSacs avatar.

That was a very good OP.

I get quite agitated when people piss on Metacritic. I think it's very useful as long as it's not seen as some absolute authority.

Metacritic isn't bad at all.