Any of the Jovian Planets.
See http://www.sciencenetlinks.com/interactives/messenger/psc/PlanetSize.html
The most massive planet in our solar system is Jupiter. It is approximately 318 times the mass of Earth.
The fifth most massive planet in our solar system is Earth, after Jupiter, Saturn, Neptune, and Uranus. Mars, Venus, and Mercury are all less massive than Earth.
The moon is Earth's natural satellite and is not next to any other planet in our solar system. It orbits around Earth.
Mars follows Earth as the next planet out from the sun.
Uranus
Uranus
The Sun is not a planet, it is a Star. It is 332,946 times more massive than the Earth.
...Venus/EARTH/Mars...
its the 4th planet from the sun but it is the very next planet next to us.
No. In our solar system it is the second most massive planet. Fifth place goes to Earth.
The moon and the planet it orbits that have the highest ratio of their masses are Earth's moon and Earth. The earth is only about 81 times as massive as its moon. In the #2 planet/moon mass ratio among the eight planets, Saturn is 4226 times as massive at Titan.
Venus is the next planet toward the Sun. Mars is the next planet away from the Sun.