Not sure how it plays on Deck (UI is pretty small scale iirc) but Morrowind is great if you like RPGs with great atmosphere that don't hold your hand, and if you're ok with oldish graphics (some famous mods make it much more palatable however). I don't particularly like Oblivion or Skyrim, they're much more generic whereas Morrowind is pretty unique in terms of universe. But then again you'd have to look up how well it runs on the Deck and whether or not you can install the unofficial bugfix mod among other obligatory things