Question About Heaven

[Minimalist]

And then at the end battle between good and evil they all lose to evil.

Not at all. Most of the pantheon dies in the fight - but ultimately good triumphs, those remaining gods set things right, and two people who had taken shelter in the world ash emerge and repopulate the world. All is set right, and it will be an age of peace.

Well...according to this guy,

Ragnarok
by Micha F. Lindemans
Ragnarok ("Doom of the Gods"), also called Gotterdammerung, means the end of the cosmos in Norse mythology. It will be preceded by Fimbulvetr, the winter of winters. Three such winters will follow each other with no summers in between. Conflicts and feuds will break out, even between families, and all morality will disappear. This is the beginning of the end.

The wolf Skoll will finally devour the sun, and his brother Hati will eat the moon, plunging the earth [into] darkness. The stars will vanish from the sky. The cock Fjalar will crow to the giants and the golden cock Gullinkambi will crow to the gods. A third cock will raise the dead.

The earth will shudder with earthquakes, and every bond and fetter will burst, freeing the terrible wolf Fenrir. The sea will rear up because Jormungand, the Midgard Serpent, is twisting and writhing in fury as he makes his way toward the land. With every breath, Jormungand will stain the soil and the sky with his poison. The waves caused by the serpent's emerging will set free the ship Naglfar, and with the giant Hymir as their commander, the giants will sail towards the battlefield. From the realm of the dead a second ship will set sail, and this ship carries the inhabitants of hell, with Loki as their helmsman. The fire giants, led by the giant Surt, will leave Muspell in the south to join against the gods. Surt, carrying a sword that blazes like the sun itself, will scorch the earth.

Meanwhile, Heimdall will sound his horn, calling the sons of Odin and the heroes to the battlefield. From all the corners of the world, gods, giants, dwarves, demons and elves will ride towards the huge plain of Vigrid ("battle shaker") where the last battle will be fought. Odin will engage Fenrir in battle, and Thor will attack Jormungand. Thor will victorious, but the serpent's poison will gradually kill the god of thunder. Surt will seek out the swordless Freyr, who will quickly succumb to the giant. The one-handed Tyr will fight the monstrous hound Garm and they will kill each other. Loki and Heimdall, age-old enemies, will meet for a final time, and neither will survive their encounter. The fight between Odin and Fenrir will rage for a long time, but finally Fenrir will seize Odin and swallow him. Odin's son Vidar will at once leap towards the wolf and kill him with his bare hands, ripping the wolf's jaws apart.

Then Surt will fling fire in every direction. The nine worlds will burn, and friends and foes alike will perish. The earth will sink into the sea.

After the destruction, a new and idyllic world will arise from the sea and will be filled with abundant supplies. Some of the gods will survive, others will be reborn. Wickedness and misery will no longer exist and gods and men will live happily together. The descendants of Lif and Lifthrasir will inhabit this earth.

http://www.pantheon.org/articles/r/ragnarok.html

It sounds like a bummer.