An awesome RPG with awesome storyline, characters, gameplay and music. It should take about 120 hours to finish the game + there should be a load of extra missions and extrabosses.
The bosses should be much more challanging than they are in most games that's released these days and the final boss should be a dude only 1 form (for a change) who would take about 1 hour to take down if you've got the most powerfull possible stuff in the game.

You should be able to make your own weapons by forging stuff etc. There should be a gigantic world map, about 400-600 different kinds of monsters and a super boss named Ultima Weapon who would be so hard that most people who tries to beat him end up throwing their consoles into the wall in frustration or something like that.

It should be a real time action-RPG and not turnbased (even tough I love turn based games) and you should be able to strike in different ways and directions by moving the right joypad in different ways (if it's a PS2 controller you're playing it with) or something like that. Your characters should be able to reach as high as level 255 and there shouldn't be any max limit for stats. The battles should require more skill than just pressing the attack button over and over again. Hmmmm... let's see... oh, yea... and there should be a gigantic rabbit in the game who give you pointless missions.

Well... I guess that's about it.