I think multiple choices that effect the storyline and ingenuity, to be very unusual yet intriguing and has a goal that drives you to play more.

Like the best all time Game I have ever played was Final Fantasy VI Same as the Final Fantasy III that was shipped outside of Japan. In Japan it is Final Fantasy VI.

The characters had great personalities and they each had a goal. You got to make choices throughout the plot and could find secret characters and I really love an evil guy with a diabolical sense of humor and meanness.

With the graphics (SNES Quality) I still play it today.