The storyline for sure it makes all the things you do in the game worthwhile.

First the story and the lore, as well as interesting/funny/cute characters. Then the atmosphere which means graphics/music (thankfully RPGs especially Japanese tend to look and sound beautiful). Then the combat mechanics as well as general systems. Then the difficulty and balance.

For me it's the World. Let me explore a World that is beautifully created with things I have never seen before. Let me interact with people and let me understand the different cultures from town to town. Let me walk to a cliff at night and in the distance see the glowing face of the devil. Let me walk to a single city, look around and see floating islands and three moons while looking at the aurora borealus. Let me see giant robots and giant monsters duke it out and literally tear each other apart and I'm not even a part of it, but I can choose to help.

Give me a new interesting, large, living, breathing World.

The story is pretty much always going to be similar to something else.

Great dynamic story, great music, beautiful environment doesn't have to be graphically intense, memorable characters, dynamic sidequests, a little mini game like building things from the ground up like the castle in Suikoden 2 or mini village in Dark Cloud 2, Inquisition did it but blew it there, it could have been more.

Gameplay. Few games have a storyline that's so good that the gameplay doesn't matter. If you've got a game with poor gameplay, then more than likely the story won't be able to carry it. Xenosaga is one of the few RPGs that has a storyline good enough to carry the crappy combat system. The second one though? Nope.

Explorable world map, good story, random battles (like the old times)... A couple of towns...  The whole wrapped in Nice graphics and music!

For me:

a.) Customization
b.) Exploration
c.) Grinding

A tie between companions and battle system.

I love a good party and having multiple options on who your party can be in, hence I am a big fan of Mass Effect, Dragon Age and Star Ocean, where there is a lot of character development between the protagonist and their companions and even each other. An solo RPG or just 3 people (or only enough to fill the party) is a bit of a turn off but I can deal with it.

I prefer action-oriented miles over traditional turn based. It makes no sense for battles to play out on a turn-based system. I know it's silly to put it into real life but you don't wait for your opponent to attack you and let them hit you without dodging, blocking, etc. I should have the ability to avoid all damage if I have sufficient skill to do so (this has recently been circumvented by healing all members of a party after each battle but my point still stands)

Actually, I think partners is more important in the end. They help me immerse into the game once you can interact and start to care for them.

Storyline and Character development. I can live with a game without heavy of customization or the world not being on a grand scale but a boring story and equally dull characters would just kill the game for me.

Characters and gameplay.