Today Windows8 (and thus RT) has Xbox Music, Xbox Video, Netflix (if you search for it) A couple of very good 3rd party DLNA clients and xbox games. (the indy games are paltry, i'll give you that) There is clearly lots of content, and it hasn't even launched yet!
That's a great start, but it's hardly competitive with iOS. Even if we assume the Xbox Video library to be as comprehensive as iTunes, we're still missing some popular iOS and/or Android media apps. Off the top of my head, does Windows RT have an app for (or equivalent app to): Crackle, Rdio, Jango, TuneIn, 7digital, Google Currents, Flipboard, Zinio, MLB At Bat, NHL Gamecentre, Slingplayer, Youtube, Kindle, Kobo, Google Reader, IMDb, Flixster, Epicurious, NFB, Vevo, BBC/CNN/CBC/CTV/etc, Rogers Anyplace TV, Bell Mobile TV, Telus Optik TV, or Plex? And this is only for Canada, there are far more media apps that are key to success in the US market. And please don't tell me you can access them in the web browser, because you can do that on iOS and Android and yet people still download the apps en masse.
I'm sure the absence of some of these will be remedied quickly. But others will only come if the device sells well enough to make it worthwhile. For a fresh launch of a new platform, this isn't a bad content library. But they priced themselves directly against the iPad so prospective buyers are going to compare it to the iPad.