Many Android tablets went with 16:9 or 16:10 ratios over the years but it makes them next to useless in portrait orientation and relegates them to video player duties alone. The iPad aspect ratio has been chosen to provide the best compromise for the different types of content being consumed and created on it. From photos to e-magazines to web content to documents and of course video content. It's really only for video content that it is slightly more of a compromise than in other areas so overall I'd say Apple got it right.
Bear in mind that in the early stages of iPad development, and probably more recently, Apple will have almost certainly built prototypes of varying aspect ratios and sizes and so they were in the best position to make that call.
Spot on!