Good point. However, there are still some things I would like to mention. The Xbox360 not only has a strong following thanks to Xbox, but it has a far superior (in sheer numbers of subscription) online system, Xbox Live. A subscription which comes free for the Xbox360. Not only that but, like the Revolution and Playstation, it is backwards compatible with the Xbox, i.e. you can play Halo 2 on your Xbox with someone who is using an Xbox360. I am not aware of this feature on either of the other systems.
Also, the Xbox360 has a number of old arcade 'hits' available through the Xbox Arcade. For a list go here:
http://www.xbox.com/en-US/community/news/2005/1014-nextgeneration.htm?MSID=99b90e6a3f074a8d94c32c0c7b273ee6. While there may not be as many it still has some, keep in mind this list will grow.
I do think that the Revolution will pose a threat to Microsoft but even if Xbox begins to become unpopular you can bet that Microsoft will do something. Something that is likely to be a viral marketing campaign. Plus Microsoft's CEO is the richest man in the world and, as show with the original Xbox, he is more than willing to spend as much money as it takes to make the Xbox profitable and mainstream. I highly doubt Nintendo will do this.
You may think me a Microsoft fan boy for the above mentioned but hey, Ocarina of Time is still my favorite game. It's just that I like the way that Xbox and Xbox360 are built (by Built I do not mean look) more than that of the Gamecube and Revolution. N64 still rocks, even if it is dead in Nintendo's corporate view.
Cheerio!