Minecraft is pretty popular around our house.... from the 6 year old to the 18 year old. I do have to admit I encourage it. There are several sites that review it... (here's one) For those of you that don't know what minecraft is, It's basically an online 'world' that allows you to wonder around interacting with the environment. It's very blocky and kids can build anything that they can imagine (including recreating architecture in the real world) Although there is no blood and gore, you do have to fight off monsters and hunt animals to survive. - There is a creative mode that prevents dying also.
One of my favorite things though is that there are a million and one things out there now to use minecraft educationally! (besides all the other products) You can learn to program minecraft - starting at 7 or 8 years old. Modify it to be the way you want! There are classes, books, and more all on this subject.
For younger kids there are chapter books and workbooks, math, science, and curriculum; all geared around learning and using the subject of minecraft. Simple searches come up with anythign you might need!
Please share anymore you find. My son loves these!