For Elder Scrolls, I'd recommend giving either Oblivion or Skyrim a whirl, and then after you feel done with one, try the other. In my opinion they are both great for different reasons, and they are different enough to feel like very different games in some ways.

If it helps you make a decision in terms of RPG story feel, Skyrim is more about you as the hero, and Oblivion you're more like a person that happens to be there.

There's great modding resources too if you're into that. Especially on Nexus. Even light modding like some QoL upgrades or bug fixes. I'm not talking crazy mods.

Oh, the endgame for Skyrim (the original DLCs) really do give you some rewarding post-game fun in like a god mode.