From the Untold History of Japanese Developers vol 3:
Wow. Now, suddenly, the focus on Janken in Alex Kidd makes way more sense.
Sega were planning on making a Dragon Ball game... I guess this happened long enough ago that it's okay for me to talk about this! The project began as a Dragon Ball title, not as a direct competitor to Super Mario Bros.
But when we were told we could not use the Dragon Ball licence any more, we were forced to come up with our own ideas instead. For example, when it was Dragon Ball, Goku fought with his Power Pole, but we changed that to a punch attack. It was only after we came up with the plan to restart the project as Alex Kidd in Miracle World that we starting thinking about Mario, and looking for ways in which to differentiate the title from it.
Wow. Now, suddenly, the focus on Janken in Alex Kidd makes way more sense.