Let's not forget the visionary aspects of Bill Gates. In the infancy of the web, which at the time was Prodigy and other BBS type systems, Bill Gates, and several others saw a future for interconnected computers and the "World Wide Web." Microsoft invested and partnered heavily with cable companies, citing that connectivity and ubiquitous computing would be the next technological revolution - and he was right. Gates, Jobs, et. all, also made computing easy by bringing the PC into the mainstream. Many of the advances in computing that we have enjoyed is due, in large part, to two generations who have been raised with at least one computer in the home.
Gates, probably more so than Microsoft as an entity, realized that the only way that computing can continue in the mainstream psyche, is with a healthy, competitive balance, that's why he gave so much money to Apple when it was teetering on the verge of bankruptcy, well, I'm sure that the anti-trust lawsuit had a bit to do with that as well, but either way, Microsoft continues to fund start-ups and heavy R&D companies, creating public development arenas like CodePlex, contributing to open source projects like Drupal, jQuery and providing free development tools like Visual Studio Express, SQL Server Express, etc.
Microsoft is also a major player in many international standardization bodies like the W3C. Many of the current standards were pushed by Microsoft and were widely adopted because Microsoft embraced them. Standards like XML, XSL, HTML and others that we see every day on the web are around because Microsoft put their considerable weight behind them.
Throughout the years, Microsoft has always espoused that developers are the key to moving computing forward. As much as I may grumble about the quality of their API documentation, the fact is that Microsoft has created an environment where programmers can build amazing programs that will work consistently on any version of Windows - something that was challenging in the early years when there were literally dozens of operating systems that came and went, and you had no supporting APIs to lend consistent look-and-feel. As a programmer with a great software idea, it is pretty easy to target and support an Operating System with a 90%+ deployment worldwide.
Sure, Microsoft had created and leveraged it's monopoly, especially during the browser wars, but those days are long past. Microsoft also has a fairly spotty record in terms of security, but again, if you were writing a virus I'm sure you would target the 90% instead of the 1-2% that Linux enjoys, or the 8% that OS-X has, it's purely a matter of scale and probability.
Microsoft, of late, seems to have lost their way, and personally, I think that it starts at the top with Ballmer. Microsoft clearly has missed the mobile device revolution (both phones and tables), their web presence is paltry compared to Google and truth be told, they are falling behind in mindshare (and maybe marketshare as well) relative to Apple and Google, especially in the web and mobile arenas. Gates, nearly 15 years ago went all-in on the networked, ubiquitous computing concept, even pumping out before-their-time products like Origami and MSN TV, which new products like the iPad and Roku/Boxee respectively, have executed better in modern times. I simply do not see the type of leadership that will usher in the next era of computing from Ballmer. There are so many products and ideas from Microsoft R&D that are withering on the vine so to speak, enough so that the Slate and Courier were both killed, years before the iPad revolution. This has led to a mass exodus of top talent out of Microsoft to competitors like Google and Oracle.
Even if Gates does not come back full time, I think that he does have to outline a vision for the future that Microsoft can drive towards. Until then, they will flounder with half-baked products like Windows 8, kill moderately successful products like Silverlight and never commercialize the ideas coming from their own R&D department. Unless Microsoft (and Ballmer specifically) stops looking at the bottom-line, capital expeditures, ROI and other Accounting geekery, they will continue to be the lumbering giant who's best days are behind them.