Soul Calibur
Underrated: Soul Calibur III
PS2 only, no Link, a serious memory card bug and unintentional gameplay imbalances for competetive players (which were fixed in the arcade edition. Alas this was the pre-patch era), but probably the most quality single player content a fighter has ever had.
A great roster, stages for all 25 characters (not counting the 17 bonus fighters) with a few to spare, an
awesome intro video, extensive create-a-character (still one of the greats, especially for its time), a really really good soundtrack (featuring
redone classics returning from Soul Calibur I and a lot of
great new tracks).
Oh, and modes. It had your arcade mode (called quick play, but functionally identical) a Missions mode (a bunch of challenge fights under special conditions or against special enemies, and things like survival), World Championship (simulates a tournament against AI), and
two story modes.
The first is Tales of Souls, which is close to your traditional arcade mode but with more narrative and player interaction. You choose one of the 24 main fighters (can't play as the final boss in this mode because duh) and set off on a journey, with text describing your characters actions (tailored to that character specifically, and though resulting in mostly the same fights, it's largely not generic). You often get to choose one of two paths, resulting in a different series of fights each time you play. Sometimes there will be a short cutscene before the fight where you have to perform a little QTE or you'll start the battle with less health or some other debilitation. Sometimes after a battle you'll get a prompt that--unless ignored--leads to a bonus fight on the same stage.
Those could get pretty crazy. You fight a boss after a set amount of stages, and then get an ending movie (with two outcomes based on the player's input). However, if you meet certain conditions, there are some secrets to be discovered, like Olcadan in the Grand Labyrinth or the hidden final boss.
The second story mode is Chronicles of the Sword. In that one, you create the main character, and the game's story takes place in a sort of different reality from the main Soul Calibur story (though Soul Edge still plays a big role, and the main cast shows up as difficult optional bonus fights). It plays out like a lite strategy game, with RPG elements (characters have classes, stats, and they level up) and fights are resolved (in most cases) through traditional Soul Calibur battles. The whole thing is pretty lengthy, and though the story isn't super amazing or anything, it's not horrible either. Frankly it's amazing that they made a fully separate story with it's own characters and all that on top of managing the Soul Calibur story and cast.
SCIII is an amazing fighting game package, and it's disheartening to see it get belittled for not having a guest character, or being on PS2. Even the balance and bug issues seem pointless to consider in retrospect, as they were both fixed in the Arcade Edition, and if the game were remastered, they would surely be fixed there as well. The meat and potatoes of the game are fantastic, and deserve more respect, especially when fighting games these days struggle to include even the most basic of modes.
Overrated: Soul Calibur II
Gets too much credit based on Link and nostalgia. It's a great game, but almost everything in it was done better elsewhere in the series.
Man I need to sleep