Microsoft's first serious attempt to enter the consumer market started two months ago with the launch of Windows 8, WP8 and Surface. It's too early to know if it's going to be successful, but clearly is not being easy.
I think the products need another iteration to reach the quality needed to compete at the same level with iOS and Android, but hopefully this breed of products is good enough to grab respectable market share.
Microsoft has to change a lot to be successful in the consumer market, for example, product cycles are too long, good thing for the corporate market but frustrating for consumers that always want the latest and greatest thing.
Another problem is the price of the products, historical margins of the pc industry are high compared to the mobile. But if Microsoft and partners prices lower the tablets, these will cannibalize the more profitable laptop and PC market.
A big advantage for Google and Apple is that they don't have this big asset to protect, they are free to be agressive and innovate, sort of, and the former more than the latter.