I would love to see a half-giant race in the core rules. I remember an early Dragon Magazine featuring an "half-ogre" race. (In my homebrew half-ogres are a playable race, replacing the half-orcs.)
Also half-giants are a fairly common archetype in fantasy fiction. (Remember Hagrid from the Harry Potter series?) The books should include rules to play them. I agree with the OP saying that the Goliaths are a little weird; I would rather have a more "generic" half-giant/half-ogre PC race present in the core books.