In my opinion, I'd rate it a solid 8. At least for the PC version.
In Minecraft, you can do basically anything you want. Really. It has loads of content. As if all the content it has wasn't enough, it's still in development.
That means that many more updates are upcoming. If the vanilla game is too boring for you, why not download some mods? Mods can add so much to your game, ranging from simple crafting edits to entirely new game mechanics.
If you're tired of building from the ground up, you can try downloading some maps. You can download adventure, parkour, horror, or even just artistic maps.
Though that's just my opinion. Many big websites also recommend it. IGN gives it a 9/10, PC Gamer gives it a 9.6/10, and Gamespot gives it an 8.5/10.
So yes, I highly recommend you get it.