Microsoft has the overall No.1[1] spot - it sells the OS and the software that virtually every office in the world (and most homes) rely upon. Nobody has come close to challenging that.
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.
[1] 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)
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.
[1] 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)