Warcraft 3 map editor was such an influential tool. Warcraft 3 map editor spawned multiple new game genres. DotA map spawned MOBAs, numerous tower defense games such as Element TD spawned the Tower Defense genre and recently the autochess genre has appeared, taking many inspirations from maps such as Legion TD.

There still are some popular map genres in Warcraft 3 that haven't been converted to standalone games, so there's still a lot of potential. Most notably I can think of are tag games.