This is an idea that frequently crops up – and is popular with many. I just watched a Norwegian production dealing with modern-day gods and giants, and in this version, the giants were maintaining that they once received adulation, from a much earlier time, before being replaced by the gods.

The Greek titans almost certainly do not represent a vestige of an earlier belief system that was supplanted by the gods of the classic Greek pantheon. Many Indo-European traditions include the idea of giants that lived long ago, often having had their own day in the sun when they were without rival. For the idea that the Greek titans were once worshiped, and that their presence in Classical mythology is a remnant of that earlier tradition, we would have to project similar “older belief systems” into the past of many other people who speak Indo-European languages and who possessed the idea of a race of giants who opposed the gods.

What we are really dealing with is an apparently widespread tradition that maintained that much of the “prime movement” of the world/universe was thanks to early titans, presumably because the scale of the work that needed to be accomplished was on such an enormous scale. According to these traditions, the titans did their work in creating things, only to be supplanted by a new generation of deities who were able to suppress the earlier giants.

We see echoes of this sort of tradition in more recent Northern European folklore, which often has giants building remarkable things, often at the request/orders of a person (sometimes a saint). The Giant’s Causeway in Ireland is typical of the sort of thing a giant can accomplish – and the scale often imagined. But there are also many churches that have attracted a widespread “Migratory” Legend that describes how a saint struck a deal with a giant to build a church. The legend if often used to explain how a log of enormous girth (greater than it seems humanly possible to move) found its way into the foundation of the structure. These legends also explain large, isolated boulders in open fields – “certainly a giant must have hurled that rock” (while in reality, they were moved there by glacial action).

These more recent legends all depend on the idea that giants were once commonly seen to walk the land, but that they belong exclusively to former times. That’s apparently the way believers in the older European pantheons viewed the titans/giants: these gigantic entities were once players on the stage, but they do not have a role in the day-to-day events of “our time.”

On top of this, there is simply no evidence of a time when the titans/giants were actually worshiped. With that, however, we risk trying to prove a negative, which is impossible. The absence of evidence doesn’t necessarily prove the opposite, but we need to take the absence as having some significance, given everything else I have outlined here.

edit: thanks for the dragon!