Since I don't play tabletop and know almost nothing about alternatives, what other tabletop system is mechanically better? Regardless of popularity. Especially if adapted to a video game crpg format.
3E, Pathfinder (basically D&D 3.75), something like Rolemaster might be interesting, AD&D 1E and 2E. WEG's D6 system... almost anything really. Lol
5E is fine, it just sucks that such a nice rendition of tabletop stuff doesn't use a better system.
A full fledged BECMI D&D CRPG would be interesting. I think they did that in... Warriors of the Eternal Sun? Game was pretty bad though.