by: David Goldman | CNN Money

NEW YORK (CNNMoney) -- Since its 2010 debut, no tablet has come close to unseating the mighty iPad.

The many contenders can all be tossed in two piles: "Me too" devices or cheaper/smaller tablets. Neither has dealt Apple (AAPL, Fortune 500) a serious blow, and the iPad Mini -- unveiled on Tuesday -- is likely to solidify Apple's dominance.

But Windows 8 offers a compelling third way to take on the iPad: by putting a full PC experience on a tablet.