They are described as quite different in the myths. For example, the Titans had much power, whilst the Gigantes drew power from their mother, Gaea. So are they the same or different beings?
The Giants and Gods are different! In the Greek creation myths, Gaea and Ouranos had multiple 'groups' of children. The first were creatures that had "shattering, overwhelming strength" and "a hundred hands and fifty heads". Then came the Cyclopes, and after them the Titans.
Cronus overthrew his father Ouranos. When he overthrew his father, Ouranos' spilled blood created the Giants (and the furies as well!).
The Gods are the product of Cronus and his wife Rhea. Cronus was told that a child of his would overthrow him, so he ate his children. Eventually, Rhea sought help with Gaea and they tricked Cronus with a rock wrapped in blankets. Meanwhile, Zeus was raised somewhere else and later overthrew his father Cronus and freed his five siblings (Hera, Demeter, Poseidon, Hades, and Hestia (not in that order)).
The Titans, Giants, and Gods all had powers and were respected in different ways, but the Titans and Giants were a product of Ouranos, while the Gods were the Product of the Titan Cronus.
So they are different beings.
Mythology by Edith Hamilton