Final Fantasy II (Famicom, 1988)

The first Final Fantasy game did well enough that exactly one year later, Final Fantasy II was released, only in Japan.  Since the first game tied up its story tightly, Square felt no need to make II a continuation of its story, so they decided instead to make it a completely original game.  The story of Final Fantasy II follows four kids who are orphaned in an attack on their hometown by the wicked Empire.  The Emperor has opened a portal to a world of monsters and is controlling them in a plot for world conquest.  One of the kids, Leon, is separated from his friends, Firion, Maria, and Gus, and the three of them join a rebel faction.
This is actually one of the better plot-lines in the Final Fantasy series, due to the way it is told throughout the game.  The centerpiece of the story is the war between the Empire and the resistance, and it does a marvelous job at making it feel like a war.  There are some genuinely sad moments when characters you've known and fought alongside with die.  Yes, this is the first entry in the series to feature themes of death and war.  For one of the less-played and discussed titles in the series, it also introduced a few things which would become standards in all titles to come.  Final Fantasy II introduced Cid, here an airship pilot who runs a ferry service.  In all of the following games he would have something to do with airships (with a few exceptions).  Also introduced are the Chocobos, giant birds that will carry you across the map if you are lucky enough to stumble upon them in the forest.
Final Fantasy II improves upon everything in the first game (despite still holding a few flaws like ineffective hits).  For the first time in the series, the story and characters were the focus of the game.  Every character you encounter has a personality and back story that weave into the plot.  There is a significant amount more dialogue here than in the first game.  Another thing that is improved is the battle window and graphics.  The first game had a revolutionary side view of the action (most RPGs at the time used a first-person view) which showed each character in your party and every enemy, with stats on the side.  There was very little animation due to the low budget of the game.  Final Fantasy II reduces the clutter by placing all of the information at the bottom, and now every different action has a different animation.  Magic users no longer have to struggle with leveled charges, because now each character has MP (Magic Points) which is spent with each spell.
The biggest improvement in the game is the leveling system.  No longer can you choose which class each character will be.  Instead, each character may potentially learn any skill, attacking, magic, and more.  Also gone are experience points, in favor of a new system which takes into account every action you take in and out of battle.  The more damage you take, the more your defense and HP (Health Points) go up.  The more you attack, the better you get at a certain weapon.  The more you use magic, the better you get at each spell.  This system is not hard to cheat though.  You can have party members attack each other to raise HP significant amounts in a single battle.  There is a glitch where if you select an action, and cancel it, the game does not un-count the action from your experience, allowing you (with some patience) to level up attributes of which you did not actually use in battle.
This system is strange to get used to at first, but it actually makes building characters more interesting than in the first game since you can make progress with every battle, and it is more realistic.  The first game featured a heavy emphasis on level grinding to progress, but this game has a much faster pace, helped by its new systems.  The Final Fantasy series likes to reinvent itself with every new installment, and even when a game fails for one reason or another, their constant experimentation is admirable.  If every game were like Final Fantasy I, I doubt the series would have survived as long as it has.