Gwyn, The Lord of Cinder
The final boss of Dark Souls is not a man with a evil mustache. Nor is he a villainous being plotting something evil. He is just a broken hero god who was once much more than what he has become. He is someone who was desperate enough to sacrifice everything to prolong the age of fire.
The Boss
Such an cinematic boss fight. At the end of MGS3, you fight your old mentor/someone Snake has cared so much for. You fight her one-on-one, with no one to interrupt the fight. After you defeat her, the ending shows why she betrayed her country(or should I say didn't betray her country), enough to make you feel like shit
Ganondorf
He is usually the final boss in every zelda game, whether in his human form or his beastly Ganon form. I had hard time choosing which incarnation i liked the best, so I just said "Oh what the hell?" and picked four. The first one is Demise, since he is considered the origin of the Ganondorf. The second version I liked was the Ocarina of time incarnation. The build up to the boss (Ganondorf theme on Organ FTW), the way he greets you, and the way he fights on in his beast form really was a great touch to the end of the game. The third version is the Wind Waker version. The music, the flooding Hyrule, Ganondorf's attacks, they all blend together very well. The last version I liked was Twilight Princess version, since this is also another kick=ass one-on-one sword fight.