I really want to play a Final Fantasy game at some point, but always seem to find something else play. Same thing goes for Dragon Quest games. I could ask everyone here which game from each series you recommend, but would I actually play it? Probably not. 😔
As for a single game I own, I will probably never play Disgaea 5. It's been so long since I bought it.
Fire Emblem (any of them). I think I would really like them, but I just don't have time to get to them. There's frankly a lot of stuff in my library which I might never get to.