I don't think this conclusion will surprise many, but despite what I'd consider some major flaws for a competitive smartphone in 2013, and besides its lack of true innovation, Galaxy S4 is probably still going to end up as a huge hit for Samsung, at least as big as the Galaxy S3 was, much like iPhone 4S and iPhone 5 were for Apple, and despite not adding anything that innovative after the iPhone 4, in both hardware and software.
There are two factors are play here that make this possible. One is brand momentum, and the other is advertising money. Although they both sound similar, they are quite different, and one without the other won't be as successful. For example, if you gave ZTE the advertising money Samsung is going to spend on promoting Galaxy S4, they would get quite a bit of sales, but they wouldn't sell nearly as much as Samsung with the Galaxy S4, because they are not a trusted company the way Samsung is right now in mobile, and their product brands are not recognizable.
Samsung spent 3 years promoting the Galaxy S brand, making customers love it, and then go out and promote it to their friends, too. Slowly, but surely, Samsung has built a large network of customers who are recommending the "Galaxy S" smartphones to their friends. That alone is perhaps even more important than the huge marketing campaigns they are going to launch in many countries for the Galaxy S4, although they do help reassure the people considering them for the first time, that they are indeed buying a quality and recognized product.
This is really no different than what has happened with the iPhones. If there's something Samsung copied from Apple is the idea that they should build a powerful and loved product brand, and then promote it all over the place.
The Galaxy S4 still has some flaws like virtually unchanged design from the Galaxy S3, which I believe was nothing to brag about either, its cheap plastic body, when other companies are using aluminum, kevlar, glass or polycarbonate. I said it before and I'll say it again. For a device that will cost somewhere between $600-$700 unlocked in US, and probably significantly more in Europe and other places, the excuse that "plastic is cheaper to use" doesn't work for me. But it does look like no amount of criticism about this is phasing Samsung, so we might keep seeing it for a long time from them.
That's not to say that the Galaxy S4 can't be called a great phone overall, but it does detract from being an even better all-around phone, that can compete with anything else out there and beat it not just in a few features, but in most or all of them.