I love minecraft ):< - terraria is in 2d, minecraft in 3d, and doesn't lag at all, and the art is 16x16, low res, but it fits perfectly with the cube world theme. Terraria isn't even realistic: it's got strange monsters, creatures, and a lot of sci-fi stuph. Minecraft is 99% realistic, apart of the enemy mobs. And the fun never ends, there are thousands of servers and at the same time thousands of awesome mods, if you are a bit bored of normal play.
For me Minecraft PwN's Terraria