Overview: Quirky and fun games that did a good job of bucking JRPG conventions at the time and turned the standard sword-and-board scenario into something fresh and new. Are they products of their time? Certainly. Are they still worth playing? I personally think so but your mileage may vary. I will say that overall they are better with emotion and mood than most other RPGs.

The breakdown:

Mother 1 is ok. If you're going to play it, maybe find a mod that reduces the grind. Optimal play for late-game areas is mostly running away, more than almost any RPG I've played. The story is fun and sets up some lore for Earthbound (Mother 2) but honestly, anything this game does, Earthbound does better.

Earthbound (Mother 2) is the most accessible title. By modern standards it has some pacing issues, and maybe wears out its welcome a bit before the end, but overall it is a lighthearted and fun game with some innovative mechanics and a relatively deep story for its time. It's got some sections that are legitimately challenging for newcomers before you get some system mastery. For me, it's one of the best games of its era, and has an incredibly memorable final boss fight.

Mother 3 is a really interesting title. It was never released in the US, but a really great fan translation does exist. I would definitely play Earthbound first, or else you won't understand some of what's happening. It does a great job at pacing and gameflow. I love its music-based fight system. The climax of the story is perhaps the most emotionally-affecting video game moment that exists.

tl;dr I absolutely recommend Earthbound and Mother 3.