The Dagda had many children. It is not easy to determine all of their counterparts in Greek mythology because the Greek Zeus had over 150 children. But there are some obvious examples.
Here is my analysis of the counterparts:
Dagda - Zeus
Brigid - Greek Athena
Aengus -unknown at this time.
Cermait - Greek Dionysus
Bodb Derg (successor) - unknown at this time.
Midir - unknown at this time.
I would equate the following Irish Gaelic Gods/Goddesses with the Greek Gods/Goddesses as follows:
Dian Cecht - God of Medicine - Greek Apollo or Hermes
Goibniu - God of the Smiths - Greek Hephaestus
Lir - God of the sea - Greek Poseidon
Lugh - Warrior God - Greek Apollo
Elatha - Father of Dagda - Greek Cronus
As I am able to find more Celtic literature, I will be able to determine the rest of the equivalents.