in norse mythology the gods are basically just stronger individuals who know the old lore, and thus can use spells, and also eat apples that reverse the aging process
i think in greek mythology if you did enough cool things you could become a godlike being, but most of the greatest heroes were already the offspring of someone zeus fucked so...Wikipedia has a list of them
in finnish mythology you have a few random ass people who gained great power and were deitified as a response. there's a few cool ones like:
-Lalli, Finn who slew St. Henry of Uppsala on the ice of Lake Köyliö, according to a legend
-Ilmarinen, the great smith, maker of heaven. Designed the Sampo mill of fortune
and a few absolute assholes like:
-Väinämöinen, the old and wise man, who possessed a potent, magical voice.
I will forever claim that he was a fucking asshole, I have read Kalevala you fucker, it doesnt paint you in a good light even though you're the main character 
and then there's Kullervo who exists only to suffer