LOS ANGELES (CNNMoney.com) - Two months ago, Phil Harrison, the president of Sony Computer Entertainment's Worldwide Studios, made a startling declaration: "If 'World of Warcraft' were a country, it would be bigger than Ireland."

It's surprising, but true. More than 6 million players pay a monthly fee (U.S. players pay $15 per month) for the game – versus Ireland's population of 4 million-plus. Perhaps even more startling is the fact that "World of Warcraft" is just a piece of the "Warcraft" empire. When you add in the first three games of Blizzard Entertainment's flagship franchise, along with expansion packs, the company has sold more than 19 million copies of something "Warcraft"-related.

"Spore," from the creator of "The Sims" is due out next year.

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Will Wright's "The Sims," meanwhile, has brought in more than $1 billion in revenue for Electronic Arts. Between the original 2000 game, its 2004 sequel and multiple expansion packs, EA (Research) has sold more than 58 million copies of "Sims" software.

Wright and the Blizzard team are two of the top members of an elite fraternity in the gaming world: Hit makers – developers whose names on the box virtually guarantee massive sales. Also in the top tier: Rockstar Games, the makers of the "Grand Theft Auto" series, which has sold roughly 40 million copies.

Hit makers are allowed some luxuries other game makers aren't – more time to fine-tune their games being perhaps the most important.

"They get to set their own schedule," said John Taylor, an analyst with Arcadia. "They don't have a publisher breathing down their neck waiting to fill a hole in the publishing schedule... A team that's in a studio – that's part of a global organization – just really doesn't have that kind of luxury."

They're also allowed to blaze new paths based on their past successes – though not all choose to do that, as seen at E3 this year. Several members of the hit maker club have a new game on display at E3 this year. And each faces a mountain of expectations.

For Blizzard (which is owned by Vivendi Games (Research)), while there were plenty of rumors that we'd see the next installment of "Diablo" (another hit franchise for the company) at E3, the company is instead keeping the spotlight on "World of Warcraft," letting attendees play the expansion pack "The Burning Crusade."

The first major expansion for "WoW" will offer new areas to explore, new quests and two new races. You'll also be able to earn a flying mount (think Pegasus or a gryphon) in one of the new quests, enabling you to fly over the expansion lands rather than walking. Advanced players will be able to hit level 70 (versus a level 60 cap in the original game) and players will have a new in-world profession option: Jewelmaker. Blizzard has not yet given a release date for the game. The end of the year is not a bad bet, but not a certainty by any means.

Will Wright, meanwhile, is exploring very new territory. "Spore," due in 2007, is an amalgamation of several genres – 'god' games, strategy titles, 'sandbox' games (open-ended titles, like "The Sims")... heck, even "Pac Man." You'll help a one-celled creature evolve into a more advanced life form, then watch it multiply and form a village, which eventually becomes a city, which can lead to space exploration and the discovery (and, should you choose, elimination) of other worlds.

Creating the creatures is incredibly fun – and challenging, in that you'll have to decide whether to spend the points you earn on physical or mental strengths. Wright also plans to populate "Spore's" world with creatures developed by other players (via download), making every gameplay experience a unique one. (He has referred to the title as a "massively single-player online game.)

Making evolution an easy-to-grasp concept is a challenge, but from what we've seen, "Spore" will reach out to the same broad audience that embraced "The Sims."

As for Rockstar (a division of Take Two Interactive Software (Research))... well, that's sort of a mystery. "Bully," the company's long-awaited next game has been delayed a couple of times now (it was originally slated for October 2005, then February 2006 and now has no updated release date) – and isn't on open display at the show. (The company says it's not showing behind closed doors either, but Rockstar is notoriously secretive at E3.)

"Bully" is certain to be controversial, as it follows the story of a troublesome schoolboy who stands up to bullies and teachers and pulls pranks around campus. Other than that, no one knows exactly what to suspect. Also, the next "Grand Theft Auto" is due Oct. 16, 2007 – but the game's not at the show.

Each hit maker faces a different level of expectation – from gamers and publishers alike. It can be a significant source of pressure, but it also helps drive them to create titles that shatter sales – and revenue – records.