There have actually been some subtle changes in the Coca-Cola logo but not nearly as dramatic as the Pepsi logos. I personally think the new Pepsi design is atrocious. They should have stopped in 1973.
UPDATE: As some of you pointed out in the comments, Coca-Cola has in fact made quite a few logo changes, and the evolution is probably not as straightforward as the above graphic suggests. No doubt there was some overlap as well as issues with stuff getting hand-drawn. There was probably a good bit of market testing in the later years too - which is why I put this in the "miscellaneous" category. In any case, here is a revised version from Brand New:
P.S. The new Pepsi logo is still ugly.