My personal stance on this is that while an RPG story doesn't need to be 'OMG- F***-S*** AMAZING' for me to enjoy it, the weaker the gameplay is, the better the story has to be. If the gameplay isn't all that great, (though it still needs to be decent, otherwise I won't bother with it,) the story had better pick up the slack. That said... at the least, a JRPG story should be bearable. If it's bearable, and the gameplay is great, then I can still trudge through it. However... if the story is absolute anus, (such as Persona 3; not everyone likes that game,) then I can only keep going if the gameplay's good, and even then, only 50& of the experience will still be enjoyable.
Let's look at an example; namely, Lunar Silver Star Story for the PSP. IMO, the gameplay itself was far from the best I'd experienced. It was somewhat slow, and the gameplay was just your basic JRPG fare, and fairly easy too. But, it was still decent. Now, if the only thing Lunar had was decent gameplay, then I'd probably have dropped it in favor of game's with great gameplay. But what separated Lunar from, say, Mario, or some other game that relies nearly solely on Gameplay, is that Lunar had an enjoyable story and a good cast of characters. (And Eternal Blue, when I played that, improved upon those elements in nearly every way.) This made the game that much better, and Lunar just wouldn't be the same without it's story&cast.
However, having a good (or decent, anyway,) story isn't exclusive to RPG's nowadays. For example, I finished the story mode of a Fighting Game, Blazblue Continuum Shift Extend, today. (More precisely, a retelling of the first game's story, Calamity Trigger.) Now traditionally, Fighting Game stories are nothing to write home about. However, Blazblue's Story Mode actually lived up to it's name; it was practically a Visual Novel, which just happened to have a Fighting Engine on hand for the fight scenes. Mind you, the story ended up being rather confusing, but there's still a whole other game's worth of story, (Continuum Shift proper,) so maybe the questions will be answered. But even then, there were still plenty of enjoyable moments, and you can really get drawn in at times, and even invested in the characters, which isn't something you'd expect to see in a fighting game. My point is though, that JRPG's are far from the only genre that has the potential for decent-to-good stories these days, and that like all of those other genres as well, perhaps it doesn't always need such a focus on story either.