You can look at their other ventures - XBox, Bing, Zune, HD DVD, HotMail, SQL Server, IE, Windows Mobile/Phone and point out that they have not 'defeated' their rivals in these areas. But these are secondary or tertiary industries for Microsoft, where their main objective is to head-off any would-be challenges to their dominance of the PC market. Eg. consoles replacing the home PC, Google rendering it obsolete, Apple breaking into office sales.
 Yes Apple is the biggest company right now in financial terms, but Microsoft's turf is still the most desirable (though not quite as glamorous)
The anti-trust action took a lot out them.
Here is an explanation from a journalist on why Microsoft isn't included in this article: http://pandodaily.com/2012/11/30/the-squid-and-the-jellyfish...
And here is one from about five years ago from Paul Graham on seeing Microsoft as no longer relevant: http://www.paulgraham.com/microsoft.html
It is fascinating to see how much Microsoft used to be feared: "'Can you name anybody that's happy about being in the same industry with Microsoft?' Mitchell Kapor asks." -- http://www.around.com/microsoft.html
I like using the analogy of potential energy to think about this 'battlefield'. Each of the big 5 (or 6 if you include Samsung) has a large amount of potential energy they may be able to use over time to grow, entrnech, and profit. In the case of Apple, Google, MS and Samsung the PE is primarily profit.
In the case of Facebook, it is primsrily the social graph. For Amazon, the potential energy seems to be scale & efficiency.
I, personally, believe profit, and the ability to continue to generate profit is a better form of potential energy because it is more controllable.