All hail Shiva! And never any other god, because god damn, cheaper cores and less AE!
Seriously though, I can't see any reason to ever ever ever ever pick any of the other gods, except maybe Ganesha here and there if you find yourself with a ton of vassals, or at the start of the game to get and maintain more alliances.
The rest of them simply have too small of an effect, and/or impact parts of the game that are rarely the limiting factor for the growth of your empire.
What he said, I totally agree.
All the other deities are incredibly underpowered compared to these two. Vishnu is only situationally useful when you are about to take on a larger enemy and need to destroy their manpower. Other than that.. the other three will never be used. Ever. (especially Surya)
On another note, here is what I am imagining.
Hindu Ottoman empire with administrative ideas. If you have a claim on a territory.. HELLO free cores Can someone add up the core discount, because I do not know the numbers without looking?