Earthbound yes, Mother no. Earthbound/Mother 2 is pretty much a remake of Mother, with basically no direct callbacks to the events of the first game, and is much more accessible gameplay-wise. It also features the more distinctive atmophere and quirkiness that the series is known for.

Mother 3 on the other hand is a direct follow-up to 2 that iterates on what it does. Having seen lets plays of all 3 I'd planned to skip straight to it but now I feel that'd be a mistake. Earthbound is impeccably well-structured with a unique, delightful tone to it that should not be missed, and does a much better job of feeding you its mechanics in manageable chunks.

EB is a mostly cohesive journey where you acquire new party members and PSI abilities (spells, basically) at a steady rate. Mother 3, on the other hand, spends its first act jumping between player characters in service in service of a more narrative-driven game, before eventually giving you a full party to work with. But then once you have this full party, the game gives you new spells at a much faster rate to make up for lost time. As a result people familiar with Earthbound are much less likely to be overwhelmed.

It's beneficial from a story and mechanical standpoint to play Earthbound first.