It's very hard to beat the traction that the Pi has. I think because it's explicitly targeted towards people without any embedded experience, there's been a lot of pressure to make things work and to make the documentation somewhat organised.

Intel made some nice little boards, but there wasn't much publicity and actually getting started with them wasn't easy at all because the docs were buried. They were usually modules designed for integration, not standalone devices.

With the Pi you can buy a kit, plug in the SD card and boot ot desktop in minutes.