A public service announcement to all the barbarians, assassins, monks, witch doctors, and wizards out there: Mark your calendar for May 15. Activision Blizzard (Nasdaq: ATVI) has just announced that it is launching its highly anticipated Diablo III on that fateful day.

The game is now available for pre-purchase and runs for a standard $60. Diablo III has already spurred considerable interest and anticipation within the gaming community, which goes to show how strong Activision Blizzard's franchises are. We're talking about a game series that originally debuted in 1996, and saw a sequel in 2000.

That means the series hasn't seen a major release in over a decade, yet gamers would brave a dungeon crawling with Blood Lords to get their hands on a copy. That's what I call loyalty. Including expansion packs, the franchise has sold north of 20 million copies to date, and some analysts expect this latest iteration to sell roughly 5 million copies.

The company is even offering the game free to gamers who are willing to commit to a full year's subscription to its other wildly popular franchise, World of Warcraft, which normally runs about $15 per month. That's a smart move to reinvigorate Activision's biggest cash cow as subscriber figures continue to slip. Hopefully it will deter some of those night elves from defecting to become Jedi padawans in Electronic Arts' (Nasdaq: EA) new massive multiplayer online role-playing game, Star Wars: The Old Republic.

Activision has incredible franchise strength, as three of its most popular series have been around for ages. The original Warcraft came out in 1994, followed by Diablo in 1996, and then Starcraft in 1998 -- all of which are still paying gaming dividends.

Take-Two Interactive's (Nasdaq: TTWO) Rockstar Games has achieved similar status. The developer's original Grand Theft Auto was released in 1997 and is gearing up for the next major installment, Grand Theft Auto V. That title still lacks an official release date, but you can expect it to fly off shelves, too.

This vital brand strength is one thing that social gamer Zynga (Nasdaq: ZNGA) lacks. It's hard to imagine that milking cows and collecting eggs in FarmVille won't get old after 10 years. Zynga might be able to keep things fresh with new titles, but those games aren't likely to be lasting brands that withstand the test of time.

On the other hand, it looks like Diablo will be around so long as Hell-spawned demons need exterminating. At that rate, this franchise might last into eternity.

While Activision is a strong American company, it's not likely to be in our latest free report: "3 American Companies Set to Dominate the World." These three names in consumer goods are poised to capitalize on growth in emerging markets and send those profits home to the good old U.S.A. Get the free report now.