#2 Minecraft

Minecraft. A world, made of cubes. Cubes that can be destroyed, mined, built in a few different game modes.
Creative. A free multiplayer mode. Blocks are destroyed in one hit and you have access to all types of blocks from the start. Build with friends and strangers alike. Huge forts, skyscrapers, robots, pixel art. The sky is the limit! It gets really fun when you come across some of the games invented. Spleef, an arena is built above water, with 1v1, teams or a 16 man free for all, fight to knock the blocks out from under your opponent's feet, causing them to fall and get wet, the last man (or team) standing wins. Frantic, fast paced action is guaranteed. Or race to climb a tower, race to the bottom of pitfalls, filled with obstacles. Or just take the logical approach, with hand built chess, connect 4, battleships and many more.
Survival, you need to pay for this game mode but it's worth it, purchasing the game also enables you to make and upload your own custom character skins to use. New stuff includes crafting armour, new weapons, furnaces and tools. During the day, collect resources, logs, meat, cloth and more. During the night, the monsters come out to play, many dangers await. Choose to fight, run, mine, build, farm, craft, destroy or just plain explore. Who knows. You may just find a diamond deposit. Fend off monsters such as, zombies, spiders, archer skeletons and the all powerful creepers.
Survival M-M-MULTTTTTIIIIII. Two words. Epic. Fun. It's Survival mode. WITH YOUR FRIENDS. Stand back to back, fending off hordes of enemies, work together to gain resources and build an abode to defend yourself in. Explore the vast world! Even take on the dreaded dungeons together!

http://minecraft.net/