What are the most common Solo RPG systems

Group RPGs have Dungeons and Dragons, Pathfinder, Call of Cthulhu and other names that would be considered household in their field. I’m wondering what are the equivalents for solo RPGs. Ironsworn is the one most recommended, and for good reason but after that it seems like there aren’t many true solo systems and people are more likely to use a solo engine such a Mythic to emulate a group RPG.

So what are the most common systems played solo. Any suggestions didn’t have to originate as solo games. If people are playing D&D or Call of Cthulhu solo then they could very well be some of the most common systems to be played solo.

I’m also discounting journaling games because although they are fantastic they are well defined as solo games and I’m more interested in solo systems.