[Pitchwife]

I take it we're talking about a scenario where none of the Rings of Power were forged, right? No One, no Nine, no Seven, and no Three.

I think Sauron probably wouldn't have enslaved the Men of Harad and Rhûn quite so easily as he did by baiting their kings with Rings, but I have no doubt he would have succeeded nevertheless. If even the Númenóreans fell for his gospel of Melkor he would have had little difficulty of passing himself off as a god (or at least his prophet) to people who never were taught any better. We're talking about Men whose ancestors never rebelled against Melkor-worship like the Edain did, there probably was a Melkorist tradition among them he only had to appeal to.

The Seven never affected the Dwarves much in Sauron's favour. Maybe the Dwarves of Khazad-dûm wouldn't have dug quite so deep for mithril without the Ring held by Durin VI fuelling their greed, and thus wouldn't have awoken the Balrog? An undiminished Dwarven kingdom in Khazad-dûm would have made a difference on the political map, I think.

And then there would be no Elven rings. No preserving a semblance of the Undying Lands in Lórien. Elrond, too, would be diminished, and Gandalf would have no Ring of Fire to help him kindle hearts in a darkening world. Like Sauron himself, the leaders of the resistance against him would be both less vulnerable and less powerful.