My favourite genre is the rpg. From terranigma, secret of mana and recently xenobalde chronicles, great!

But what is the most important element that defines a great rpg?

For me it's music. If the music is great then other things can be a little less appealing. For example, chrono cross. A good rpg but not great in my opinion, but the music was beautiful.

What's yours?

Storyline and Characterization! Jrpgs are the type of rpgs that I play the most and generally, they intend to be veryyyy long and if it doesn't have a good storyline + characters to keep me interested, I won't bother playing it

Music is an important factor but personally I think the most important factor is character depth.

You need good characters. Ones with lots of personality, emotions, feelings and etc. Without that, you don't have an RPG in my opinion.

EDIT:(Obviously a story as well)

Music and gameplay.

Story! By far!

RPG's live and die by their story. If they don't have a compelling narrative, then there is no point in subjecting yourself to the grind...

ofcourse the story. But just like in Xenoblade chornicles, the story became somewhat mweh after 25 hours, but the music in certain long and large areas was so good that it didn't bother me that much.

No random enemy battles as you walk around bullshit. ( when you can see them around you and avoid if I want.)
And deep awesome story.

Ah yes. That's very true.

A battle system that I can spend tens of hours with without getting bored.

And secondly, a shit ton of things to do. I like being overwhelmed with things to do at the start of a big RPG

Exploration and stuff to do in an interesting world. I want to see some cool shit apart from the story pieces.