EarthBound was the first JRPG I ever completed and the first JRPG I ever enjoyed. Before it I'd never been able to get into JRPGs: there was just too much complexity while also having too little going on. Wandering an overworld only to be randomly pulled out of it for no apparent reason was maddening. As a kid, trying to piece together the backstory of some undefined thoroughly detailed fantasy world while also taking in the emerging plot in the opening sequence wasn't anywhere near as appealing as firing up Mario or Mega Man and getting straight to the action.
EarthBound neatly sidestepped all of the things that had stopped me from liking JRPGs. The equipment system was simple without being braindead. The setting was a pastiche of suburban life that I could easily understand. The stakes were high but the tone was still whimsical and amusing. And above all I knew why I was suddenly getting dragged into battle with a snake or a crow or a dog instead of just being clotheslined by combat.
EarthBound still is my go-to recommendation in the (increasingly unlikely) event that someone says "I've always wanted to get into JRPGs, what should I start with?" It is the perfect "intro to JRPG" game without feeling trivial or like it cannot stand on its own. It singlehandedly made me love the JRPG genre, and I probably would not have played literally every other JRPG I've ever played if it wasn't for EarthBound.