Really?
Fire Giant can be learned on 3rd level, and is stronger then 5th level Fire Elemental
Ice Lord (water giant) can be learned on same level as Water Elemental (lord of sea) and is much better.
Only Earth Elemental seems a bit better then Stone Giant (due to Treamor), but it is 7th level spell, compared to 4th for giants.
I haven't seen spell needed for Storm Giants, but by looking at their stats in XML files, they also appear superior to other elementals.