Cain gave grain, while Abel gave meat.
Poseidon gave water to Athens, while Athena gave the olive tree.
Shem, I think, gave a lamb vs. the wheat of his brother.
Horus and Set, IIRC, had a similar contest to Geb.
Any other examples of people competing to offer the best gifts to the gods, or vice versa? Can you clarify the ones I don’t have quite right?
Not quite the same, though. In the other examples in the OP, the competitors were offering different gifts to the same god. Elijah and the Baalites, though, were offering the same gift to different gods.