Critics have to write about SOMETHING...
The fact is that Microsoft is not Apple (nor Google, et al).
Apple's customers are loyal and upwardly mobile (have more disposable income than most). They are, not necessarily tech-savvy, but they are CONSUMERS. They are willing to pay for style as well as substance. Apple wants to provide them with a complete ecosystem and wants to keep them from straying from that ecosystem. Apple provides these customers with appliances -- not necessarily tools.
Microsoft customers are 1) OEMS who are competing for customers buying commodity computing products -- many of whom are more technical than most -- and 2) enterprise customers who are generally tech-savvy and who buy with TCO/ROI in mind. These customers look for value in functionality and productivity -- not style.
Like Apple, Google is a consumer-oriented vendor which has little to offer to the enterprise. Its business model gives consumers software for free in exchange for making its demographic information available to people who want to sell users stuff.
Linux is "free" (well, Linux LICENSES are free) but Linux requires far too much technical knowledge to find itself being adopted my many consumers. Enterprise customers buy vendor support and have lots of technical support in-house. They chose Linux for its strengths -- not its price.
Microsoft sells a handful of consumer products via retail channels but that is not where their bread-and-butter lies.
As for the ongoing saga of Microsoft's future, market-share and profitability speak volumes about its future. No, Microsoft will not stay on top forever but none of the current players are competing directly against Microsoft either. Its inroads are in niche markets aimed at consumers. As long as its offerings run on Windows computers, and as long as Windows computers are available at competitive prices, consumers will demand that OEMs offer Windows computers. This guarantees enterprise employers a virtually unlimited supply of potential employees who can sit down with a Windows computer and be productive with little or no training.
To dethrone the king, you have to play on the king's turf. Today, no one is playing on Microsoft's turf.