Being an avid fan of mythologies, my 4th year thesis paper is about Norse Myth, I can't help but compare.
Ragnarok Online + Ragnarok Manwha + Ragnarok the Animation vs. Norse Ragnarok Myth.
For one, the word 'Ragnarok' signifies the end of the rule of gods and start of humanity. This will be triggered by the death of Baldur, son of Odin. All the gods and goddesses of Asgard, led by Odin, will fight against the Giants and other creatures led by Loki. The world will be engulfed in flames then after the world has recovered, a couple will start to repopulate the world and thus starting the rule of man. The funny thing is that they know it's coming and they are damn well ready for it.
On the side of the game, manwha, and animation, 'Ragnarok' is being prevented by the gods because they do not want their rule over the world to end. I'm not sure of what will trigger this on the GMA side but it seems that Chaos or 'Baldur' is trapped inside a human body after being 'reborn'. Along with him are Iris Irene, cleric from Payon, Fenris Fenrir, warlock who is supposed to be a 'bad wolf' on the myth but is portrayed as a hot smexy warlock who is apparently searching for Baldur's 'God Body', Loki, suave assassin and again is supposed to be the leader of the 'baddies' but he is not, and Lidia, a thief. The gods are, apparently, divided. Odin and Freya are apparently good. The rest of the others are either humanized or evil. The protagonists are the 'Valkyries' which are supposedly collecting good and brave warriors that have fallen in the battlefield.
Gladsheim or Glast Heim (place of joy) on RO is supposedly the place where the gods&goddesses gather to debate is pictured as the undead's sanctuary and houses one of the meanest badassed boss in RO..
Oh, and did I mention Odin's faithful ravens are 2 girlies calling themselves as 'The Beholders' bringing doom to all?
So I say that there is no relation of the original myth to the G-M-A at all. Don't try to inter-relate them. Just don't.
Maybe I'll go rant about Age of Mythology and the actual myths involved.