Species: There are 3 main species of giant gouramis, giant gourami (Osphronemus gorami), Siamese gourami (Trichogaster pectoralis) and kissing gourami (Helostoma temmincki).
Sorry piggy, siamese and kissers are not classed as giants, they do get a lot bigger than your average Trichagaster Leeri(pearl) or a moonlight(Trichagaster microlepis). The documented species for giant gourami:
Osphronemus goramy, common
Osphronemus laticlavius, red tail
Osphronemus exodon, elephant ear
Osphronemus septemfasciatus