At long last, digital distribution outlet Steam has joined NPD and Direct2Drive in providing weekly sales data, providing for a wider view of the PC gaming landscape.

Of course, there's a twist. Steam lists its weekly sales by revenue, instead of unit sales, so comparisons between NPD's retail charts and D2D's downloads aren't valid. Regardless, it's more information than we had before, which is always nice.

Charts for the week of 5/24 - 5/30 follow below. Remember, NPD only tracks retail sales in North America, while Steam and D2D provide a glimpse of worldwide download sales. Lastly, expect The Sims 3, which hit on June 2, to dominate next week's listings.

NPD's Top Ten (5/24 - 5/30)

1. The Sims 2 Double Deluxe / EA Maxis / $20
2. World Of Warcraft: Wrath of the Lich King / Blizzard / $39
3. Spore / EA Maxis / $40
4. World Of Warcraft Battle Chest / Blizzard / $40
5. World Of Warcraft / Blizzard / $20
6. Empire: Total War / Creative Assembly / $49
7. Reel Deal Slots Adventure / Phantom EFX / $20
8. Civilization IV: The Complete Edition / Firaxis / $40
9. The Sims 2 Apartment Life Exp. Pack / EA Maxis / $20
10. Left 4 Dead / Valve / $29

Direct2Drive's Top Ten (5/24 - 5/30)

1. BioShock / 2K Boston, 2K Australia
2. Civilization IV / Firaxis
3. X-Com Complete Bundle (UFO Defense, Terror from the Deep, Interceptor, Enforcer, Apocalypse) / Take-Two (Publisher)
4. The Sims 3 (Pre Order) / The Sims Studio
5. Delta Force: Xtreme 2 / NovaLogic
6. Sid Meier's Railroads / Firaxis
7. The Sims 2 Double Deluxe / EA Maxis
8. Civilization IV: Beyond the Sword / Firaxis
9. Civilization IV: The Complete Edition / Firaxis
10. Sid Meier's Pirates / Firaxis

Steam Weekly Top Sellers (by revenue, as of 5/24 - 5/30):

1. Team Fortress 2 / Valve
2. Killing Floor / Tripwire
3. Left 4 Dead / Valve
4. Counter-Strike: Source / Valve
5. Plants vs. Zombies / PopCap
6. The Orange Box / Valve
7. Unreal Deal Pack (Unreal Gold, U2, Unreal Tournament, UT2004, UT3) / Epic
8. Unreal Tournament 3 Black / Epic
9. Assassin's Creed / Ubisoft Montreal
10. Call of Duty 4: Modern Warfare / Infinity Ward

Special thanks to everyone who notified us of the Steam Weekly Sales chart.