Their lack of success with movies & TV on the iTunes Store isn't surprising as the market is huge, immensely valuable, well established, and populated with lots of players. A repeat of what happened with music isn't in the cards, if for no other reason that the content suppliers are already aware of what happened in the music industry. That doesn't mean that the AppleTV can't succeed though... on the contrary, if all the other content providers are able to run their own software on the AppleTV then suddenly the sky's the limit.
Hulu? There's an app for that.
Netflix? There's an app for that.
Apple will compete in delivering content alongside everyone else (hence their movement toward building a cloud), but they will sell the device and get their cut for each app sold. Big subscription players will give away their apps for free, just like Kindle, Kodo, the various internet radio apps, Skype, newspapers, magazines, etc.
A wild diversity of apps will appear on HDTV displays everywhere, and while Apple could conceivably ship their own line of TVs, I would not expect them to look upon that as the key to their business model... it would be more of a sideline much like their current display business is. Some people just like to buy Apple product, but the real win is that little $99 box that everyone will want when all the content sources make an app for it.
Apple will likely support an optional subscription payment system through their store as well, taking a small cut for the convenience of using their account system and the slick integration. This might be why magazine subscriptions are having issues with approval through Apple right now -- because Apple wants to move everyone to a unified model. No doubt the business models need to be worked out, but really Apple only needs a really tiny cut of each in order to make huge amounts of money. To all the app developers and content providers, paying a tiny percentage (note that this is different than the 30% cut that Apple takes for apps) is worthwhile because Apple shoulders the various IT tasks and they just get a cheque each month from Apple. Apple is no doubt trying hard to negotiate a good deal for themselves, but the reality is that if they want their platform to succeed, they need to make it attractive to all the providers. So giving the content providers options like "tiny percentage" vs. "flat fee", giving up any say on subscription pricing, and stepping back from policing content will be essential... and I believe inevitable for Apple. Certainly not all content has to go through Apple's servers, although they will happily provide that service to content providers as well.
Games follow naturally from this model just as they do on the iPhone/iPad. An A4 platform is not going to be able to compete technologically with the likes of XBox360 and PlayStation3, but it doesn't have to. Just like with the smartphone, games come along for the free ride. They will be better than PS2/XBox era games (more like Wii), but since the box is already there for other uses then having games available just becomes an added bonus. The biggest question is the control scheme, but if it has bluetooth then a wide array of possibilities opens up for those who want to get a bit more serious. As long as the basic control that ships with it is at least minimally functional then it will take off as a casual games platform. It also becomes an attractive platform for service providers like OnLive.
Other interesting possibilities would be leveraging the presence of a Mac/PC. The AppleTV will require that you have a computer networked to it, and that means there is the potential to use it as a storage cache. Perhaps even as a transcoder. A PVResque app provided by a streaming content provider could be told by the user to download some content to the computer to be watched at the user's convenience... potentially getting around issues with insufficient bandwidth.