Jeff Strain, co-founder of Guild Wars developer ArenaNet, has said that MMO studios should focus on creating new worlds instead of basing games on books, TV and films.
Speaking at the Leipzig GCDC Strain said, "Even the big two [franchises] haven't lived up to their expectations."
He went on to point out that the top two MMOs are based on original worlds - and that this means their creators aren't restricted when developing titles.
Strain also argued that most MMOs fail because of the social nature of the genre, and because gamers rarely commit to more than one at a time.
"The primary factor that determines whether an MMO lives or dies is the active player base," he observed.
"There's a sweet spot, and those that don't reach that threshold tend to die within a short time."
Of course, Strain continued, there are plenty of reasons why players stop playing an MMO. But he reckons you can spot potential problems before a game is even on the shelves: "Releasing an MMO before everybody on the development team is absolutely proud of it is walking away from every dime you've invested in it."
Strain agreed that World of Warcraft has had a huge impact on the industry, but warned against trying to copy Blizzard's work too closely.
"The best-placed people to create World of Warcraft's successor, it's the World of Warcraft team," he told the audience. "Let's all do our own thing, and be good at it.
"[WOW isn't] the most innovative product on the market, but it has a tremendous amount of content in it and it's exceptionally polished. It was in development for five years and probably cost well in excess of USD 40 million to bring to market."
To finish up, Strain took a swipe at the notion that monthly fees are the only payment solution for MMOs. "Don't count on subscriptions. The subscription model is not the future of the games industry," he stated.
"Gamers don't buy the argument that an MMO has to charge a subscription fee to cover the ongoing cost of servers and development. We know it, and they know it."