Looking for good local co-op RPG's

Secret of Mana on an emulator :D

How To Survive!
Not exactly a RPG, but a great co-op game, with crafting and combat stuff.

Secrets of Grindea

but it's early access

Divinity Original Sin

Also

RPG's like Secret of Mana, Pokémon, Zelda.

Aside from SoM, I wouldn't call those RPGs.

PS: use the search function to look at the 20+ threads asking for advice on local co-op games.

Tales of Symphonia (with the unofficial TSFix patch) is only $5 during the Winter Sale, and while exploration is single-player players 2-4 (if enough people are in the party) can be controlled by other players. Tales of Zestiria is a newer game in the franchise with the same co-op features, but though it's on sale too and prettier-looking, it's also kind of ass.

Binding of Isaac Rebirth, which is kind of a classic Zelda meets bullet hell dungeon exploration game, has some form of co-op, although P2 plays more like an assist than anything.

"tales of" series games are co-op in the fight battles. check them :)

If Isometric aRPG's are to your liking, I'd say give Victor Vran a go. It has local co-op, and I enjoyed it a fair amount. Has good voice acting, some entertaining dialog, and is quite fun coming up with unique builds.