The most-played PC game over the last 12 months was League of Legends, according to DFC Intelligence.

The gaming industry research firm extrapolated usage data from more than 21 million users of game server browser Xfire.

According to the research, League of Legends was the most-played game in North America and Europe, with nearly 1.3 billion hours of gameplay logged. In second place was World of Warcraft, with 600 million hours of gameplay registered, not including Asia.

“The fact that online games such League of Legends eclipsed more than a billion hours of online game time in a year is simply incredible, and a testament to the fundamental shift currently sweeping through the games industry,” said David Cole, CEO of DFC Intelligence.

“By comparison, Bungie recently announced that the Halo franchise surpassed two billion hours of online play, but that’s over a period of seven years.”

Just 45 days after release, Diablo III had been played for 172 million hours.

“Usage of course declines after launch, but it is still doing quite well and may surpass World of Warcraft in usage over the next year,” said Cole.

The full list of total US/EU play hours (July 2011 thru Jun 2012):

1. League of Legends: 1,292,502,456
2. World of Warcraft: 622,378,909
3. Minecraft: 371,635,651
4. Heroes of Newerth: 184,520,156
5. Diablo III: 172,907,605
6. Battlefield 3: 171,852,550
7. MapleStory: 165,503,651
8. StarCraft II: 163,980,293
9. World Of Tanks: 145,702,931
10. Call of Duty: Modern Warfare 3: 126,754,082