I'm going to keep this short. Despite horrible hardware failures, the xbox 360 is a good console with a good ecosystem of quality games. In a lot of ways, that's all that matter.
However, there are two factors that should prevent anyone from calling it a success. Each by itself is enough to consider the xbox/360 not-a-success. Combined? An epic not-a-success.
First, its been a massive money drain. I couldn't find a total amount, but it appears to be around the $10 billion mark. Christ, even the Pontiac Aztek could have been successful if Pontiac subsidized it that much. Yes a console SHOULD be a loss leader - but the point of a loss leader is that you make your money somewhere else.
Before anyone talks about long term plans, I'm very skeptical that, in the video game business, you can see this as a long term position. Your success rests solely on your current console. If history is any indication,I'd bet that one of the big three (Nintendo, Microsoft or Sony) isn't going to make it out of the next generation (it wasn't that long ago that Sony wasn't a player, and it was even less long ago that Sony wasn't in last place).
Secondly, they are barely in 2nd place in a 3 man race. Or, put another way, they are almost in last place. And they are stupidly behind first place. We are essentially watching two fat kids racing Usain Bolt. They also aren't really trending anywhere. In fact, data seem to indicate that Sony is gaining a little bit each year (though I do expect Kinect to address that)
The lesson shouldn't be that Microsoft understands consumers. Rather, the lesson should be that Microsoft understands that consumers have a limit on what they'll pay for goods. Oh, and that in a fierce competition that'll hang around the back.
If that's success, I'm glad I'm not successful.