I think it depends a lot on your use case. If you just want a dirt cheap HTPC, then yes, there are lots of SBCs that will fit the bill, but the RPi also has a hardware add-on ecosystem around its particular camera and GPIO/SPI/I2C/I2S availability, and even though lots of other boards have those things available and broken out too, you're going to have to be willing to do a lot more leg work to get it all hooked up properly and working for a different SoC.