They're only HD because the screen sizes are gigantic now. iPhone 5 has one of the highest PPI.
There are a lot of android 4.3 inch smartphones with HD screens, there's even a Sony Xperia 4 inch, same as the I5, HD (Xperia J).
And FYI, the Galaxy S3 in only 1 cm bigger than the I5, that's not GIGANTIC