3 million devices is pretty good. The phone isn't sold as a subsidized, lock-me-to-an-expensive-contract device.
It is sold as a standalone device and is only available to UMTS network subscribers. Most people are buying it largely on faith since it is fairly difficult to get your hands on one without purchasing it first.
3 million isn't iphone numbers, but the iphone doesn't have to compete with a dozen other types of phone.
Unless you live in the US. One of the major carriers, t-mobile, has it and you can go in store to play with one.