Moons don't produce light.
Europa is Jupiter's brightest moon. This is because...
it is brightest when it is a clear night and no stars or nothing blocking the moon in outer space
Venus is the brightest thing in the sky, after the Sun and Moon.
The sun and the moon are not planets. The sun is a star and the moon is a natural satellite. The brightest planet in Earth's sky is Venus.
The next brightest body in the sky, after the sun and the moon, is the planet Venus. The brightest star is the one called "Sirius", in the constellation "Canis Major".
The moon Io looks the brightest from the surface of Jupiter. That's because Io is the closest moon to the planet. Io is the moon on the left of the planet.
Venus
Europe
brightest
Neither. they are about the same
Murcury
After the Sun, yes.