Well, to be honest, we can have a good discussion about this.
Fleming once said, that Bond can never wear just any watch, it must be a Rolex. I mean, I'm not a Rolex fanboy or anything, but I guess that's understandable seeing that Fleming himself wore a Rolex. Had he worn a Seiko, it might just be plausible that the most copied and iconic watch in the world right now would be a 6105!
(not to say that Bond had not actually worn a Seiko. Roger Moore had the "honour" (depending on which side of the fence you're eating the grass from) to don a few Seikos in a few Bond movies).
And how the Rolex subsequently became an Omega, starting with Goldeneye is something that we all could speculate until the cows come home, but I don't have a problem with that. After all, I've got two Omegas inspired by none other than the Bond films themselves.