Developer: Markus Persson
Release date: TBA (currently nearing the end of the Alpha phase of development).
Price: 10€ (will increase to 20€ as the game moves towards completion)
So yea, this game has graphics better than Crysis.
Alright so that's out of the way.
The game itself is a pure sandbox. In the sense that there are virtually no objectives. In it's most basic form, it is a virtual construction set where players can create/craft all manners of items. Think of it as the virtual equivalent of Lego... the player gets many different types of blocks and has to use his creativity to make whatever he wants. It could be a house, a car, a castle, a city, a rocket... anything. The only limits are your imagination and of course, how much time you can dedicate to it. The game world is procedurally generated, and the map size equals twice the surface of Earth.
There are 2 versions of the game, a free version that can be played in the browser and a premium version which can be downloaded as well. The free version is basically just the construction tools where you are dropped into the map with infinite resources and you can create whatever you wish to with them. It can be played here - http://minecraft.net/play.jsp
The premuim version has more gameplay elements in it. Your resources aren't unlimited like in the free version. You have to explore the world above the surface and in underground mines to gather resources. This version also has hostile creatures populating the game world and you have to avoid them. It has a day-night cycle, where it is safe to roam the world during the day but at night it is essential to find shelter to avoid getting your face eaten off by zombies and skeletons and spiders and other dangerous beasts that roam the world. The premium version also has crafting, which allows you to create tools and items out of the resources you gather, which in turn can expedite the process of gathering. You can also craft weapons, armor, and useful items like torches and compasses. The various resources that can be gathered and used for construction or crafting include dirt, stones, coal, ores etc. while you can also pick flowers and hunt animals for food and wool, leather etc. for armor. It also has work in progress multiplayer where multiple people can go on a server and go exploring caves or mines or just screw around building things (something akin to Garry's Mod).
That's basically the game mechanics. The entire game is highly dependent on the player's creativity to imagine and construct fantastic structures and items. Some of the work can be seen here - http://cubicworlds.net/museum/gallery.php When the game starts for the first time (especially in the free version), it's a little difficult to understand what needs to be done and what can be done, but a little research on the Minecraft forums or youtube or any of the multitude of other PC gaming forums will provide enough ideas to start exploring your creativity in the game.
The game is currently an indie darling and one of the most successful indie games ever on the PC. The creator has sold about 170k copies and earned over 2.2 million dollars from the game, and he continues to earn an average of 50,000€ (Rs. 30 lakhs) every day. If for no other reason, it's at least worth checking out why so many people seem to love the game.