You've heard of, and maybe rode in, what are deemed "luxury buses" in North America; they have comfier seats, personal TV screens and maybe a cleaner washroom.
Compare those buses to what Willer Express of Japan is offering and you'll be floored. Willer Express has extremely decked-out buses, each with 12 "cocoons" designed for comfort. Each of the "cocoons" feature personal entertainment systems, power outlets, free Wi-Fi and seats that recline up to 140 degrees (try even 30 on a Greyhound) -- all in the privacy of nicely partitioned spaces. And oh, they're all window seats.
The Willer Express bus line currently only runs from Tokyo to Kyoto/Osaka, and a one-way ticket will cost you about $130, which is much cheaper than the bullet train for the same trip.
However, luxury buses are still buses, and a trip will still take 6 to 7 hours, compared to the bullet train at around two.