Zeus, Posiden, Ares all dead now what? How does the world function now?

actually, by Greek mythology, immortality means never dying of any means. Chiron the Centaur is immortal, being a son of Cronus, so when he is struck with hydra blood poisoned arrow of Hercules, he can not heal and can not die so he has to suffer the pain until he trades his immortality to Prometheus. Brothers and sisters of Zeus were swallowed by Cronus but they did not die. Hephaestus was thrown down from the top of Mt. Olympus when he was an infant, he merely broke his leg (which never heals)

people didn't stop praying to the greek gods. even today, there are still people who worship the greek, norse and egyptian gods. worshippers went underground for centuries. only now in modern times can they resurface without fear. and there are new converts too. look up neo paganism. it comes in many flavors, including the greek variety and worship of the olympians.

That's exactly what it means. Pagan gods are just that; they are not the one true God. They're part of a past age when humankind prayed to things like the sun, the moon, and the stars, not a central creator. To quote Wikipedia: "The term pagan was historically used as one of several pejorative Christian counterparts to "gentile" (גוי / נכרי) as used in the Hebrew Bible—comparable to "infidel" or "heretic". Modern ethnologists often avoid this broad usage in favour of more specific and less potentially offensive terms such as polytheism, shamanism, pantheism, or animism when referring to traditional or historical faiths." And there you have it.

Yeah, I was wondering what happened to the other gods as well.

As for the poster who states that the gods were not immortal in this movie, there are different degrees of immortality. What is commonly thought of as immortality is actually the highest degree and is termed "absolute immortality", which means that the immortal can't die by any means. The Olympians, Hades, the Titans, the Protogenoi, and many minor gods (like Morpheus) actually displayed this kind of immortality in the Greek Myths, so I'd give that poster where credit is due.

However, the immortality that is portrayed by the gods and Kronos in this movie (and various other "Greek Myth" adaptations such as Marvel, DC, God of War, Percy Jackson, Star Trek, Xena & Hercules, Supernatural, and Immortals), is that the characters never age, thus they're immortal from dying of natural causes, but are still capable of dying via other means (in Percy Jackson's case, the gods are nigh-absolute immortal, but they're still capable of dying via people not having enough belief in them. It's called "fading" rather than dying though). Not only that, other species of "immortals" have displayed this kind off immortality since ancient times (i.e. vampires, immortals from highlander, Norse gods, Egyptian gods, demons, angels, werewolves and hybrids from the Underworld series, elves, liches, dragons, yokai, etc.). The funny thing is that despite all of these being capable of dying, they are still immortal. It's just they lack the highest, "absolute" degree of it.

Welcome to my Nightmare- Freddy Krueger