"Using entertainment value as a definition still has the same problem that sales numbers have. I.e. sales numbers can change without the game changing. Sales numbers are influenced by advertisement, prices, network effects, etc.So lets look at these other factors influencing sales numbers. I totally agree on the strong influence of pricing. Free2Play games will inherently have more players than monthly subscription games. But if you look really, really careful, you'll notice that Nils performed a clever bait-and-switch trick here: In my post I specifically state that I am talking only about SUBSCRIBER numbers, not sales, and that I'm only considering games with a monthly subscriptions. I'd say the differences in subscription prices of most existing monthly subscription games are small enough not to hugely skew the measure. And with the most popular game being one of the most expensive, one can't really argue that people were drawn to this game by pricing.
Sales numbers, as well as popularity are influenced by a lot of factors that are not inherent properties of the game. Now, in my opinion one property a good definition of “good game” should have is that it is not significantly influenced by factors that are outside of the game."
The second factor is advertising. It has been repeatedly argued that World of Warcraft is more successful than other MMORPGs due to Mr. T Mohawk TV spots and other advertising. Now advertising certainly works in getting people to buy things, or in the case of MMORPGs with free trials to try those games. But that is all advertising can do. Once the player steps into the virtual world, the effect of advertising ends, and only the quality of the MMORPG determines whether the player stays or leaves. When Blizzard revealed that only 30 percent of players who do the free trial get past level 10, industry insiders admitted that 30% was actually a rather high number, and for other MMORPGs that number might well be below 10%. This is why I didn't argue with sales numbers, but with subscription numbers: If a players plays World of Warcraft for thousands of hours, and pays his subscription fee every month, we can be rather certain that advertising did not play a role in his decision to keep playing. Other games, e.g. WAR, had huge advertising budgets as well, and that only resulted in huge initial sales, and two thirds of players leaving after the first month.
The final item on Nils' list is network effects. That is a rather nebulous term which is used too often on the internet. For example it would be easy to claim that WoW has *less* network effect than EVE, because there are only 20k players on any given WoW server, while there are 350k players on the EVE server. Many MMORPGs have a large number of servers, and those are localized. I know a lot of people in the US via my blog, but I rarely meet them in a major game, because most games have completely separate US and EU servers. Apparently people rather have a few milliseconds lower ping than playing with their international friends. So do we really believe that "network effects" can make people play a game they hate for years, just because their friends play it? Furthermore I do not subscribe to the theory that network effects are not inherent to a game. Games can be good *because* they foster good networks.
This whole discussion would not be there if World of Warcraft wasn't such a huge success. Some people do not like World of Warcraft, and that is totally normal. An even larger number of people played World of Warcraft for several thousands of hours, and burned out, and that is totally normal too. What isn't normal is that many of these people are unable to talk in terms of personal choice: For some strange and twisted reason they feel the need to claim that World of Warcraft is a bad game, "dumbed down for morons", etc., to justify that they don't play WoW any more. As they can't admit that they quit WoW for personal reasons, they are constantly arguing against the fact that World of Warcraft is a very good MMORPG, and invent millions of reasons trying to disconnect it's evident success from it's quality.
I think that is quite disingeneous and unhelpful. What it leads to is a rather stupid tribal mentality in which fanbois of different games shout at each other and claim their game is "good", while the game of the other is "bad". It actually prevents us from helpful constructive criticism. It is only AFTER you admit that World of Warcraft is doing many things right that you gain credibility in discussing where WoW's flaws are. And World of Warcraft has many flaws, which are well worth discussing, in the hope that either WoW improves or a future MMORPG does better than that. The people who claim that World of Warcraft is nothing but "the lowest common denominator / dumbed down game for idiots / same as Farmville / only successful due to Mr. T Mohawk advertising / etc." are not any better than the other extreme of developers making bad WoW clones in the hope to make a quick buck. Praising or dismissing a successful game as a whole simply doesn't advance our understanding of what makes a good game. Anybody who believes that a game could earn a billion dollars a year without actually being a good game ultimately only supports those who are trying to make money with bad games.