Most? It's true of the Greeks. It's true of the Romans after their mythology is unified with the Greeks, and there's a good chance it was also true before.
But that's it, as far as I see. It's not true of Celtic mythology and Slavic mythology is barely known.
Celtic mythology doesn't have a sky god on top, it's true. But it has the same issue as Norse mythology: in the form we know it, it's much younger (and probably influenced by) Christianity.
In some sense, talking about gods in Finnish mythology is a mistake. The entities now understood as gods were not the same kind of big important guys as Indo-European gods. Finnish mythology was more focused on spirits, most of which had narrow and/or local domains. "Gods" were more like spirits with wider domains.
Then there is the confusion around names Ilmarinen, Ukko, and Jumala, which possibly referred to approximately two entities in total. And to make the matters worse, "Jumala" and "jumala" in modern Finnish translate as "God" and "god".
Or that could just be what people remembered centuries after the pre-Christian Finnish society was gone. Very little about that society is known. The traditional treatment of Finnish history is mostly based on archaeological evidence until the semi-mythical Swedish Crusades.
But he may not always have been. In most European mythologies, the thunder god is the most "in charge". In Norse mythology, the thunder god is the son of the chief god instead. My assumption is that Thor was the main god until they syncretistically tried to incorporate new beliefs about "the father and the son" and self-sacrifice on a tree, which even by this super-early mention of Odin, was over 500 years old.