imo i wouldnt choose a greek god purely on thier heros. They are fairly similar, although some are a bit better than others.
archaic heros are all the same, walking heros.
classic heros are archers, hades gets chiron, who is a bit faster as he is a horse man, the other two possy and zeus get walking archer heros.
Heroic heros, zeus + possy both get walking heros, possy gets a faster weaker hero. Speed is good but. Hades get a dude on a horse who is strong and fast.
Mythic heros, zeus get a strong and fast guy riding a crazy pegasus, it can jump attack onto any unit and jump far. It is arguably the best hero there is.
Possy gets a big ass hero that is slow but very strong. It can hit units with a special attack with its club and sends them flying.
Hades gets a guy that can turn any myth unit to stone with its special attack. Apart from that he is pretty average.
My suggestion is to try a greek god you like, say if you want to use hopliets go zeus, horses go possy or if you like archers alot use hades. The different gods are not game changing, just a nice touch.