The Space Jockeys are the mysterious pilot species first seen in the original Alien movie. Throughout the series, there have been many iterations of them, including the Engineers from Prometheus and the Mala'kak pilots from the Alien books and comics. Some of them looked ridiculous and several were asleep for millennia. Many of them died in encounters with the Xenomorphs, humans or even Predators. Here is a list of the different individual Space Jockeys, ranked by their accomplishments, their ability to survive their endeavors, and other factors.
The peasant Space Jockeys lived a simple life on the Engineer planet (known only as Planet 4) and raised wheat. Their lives were uneventful until David arrived on the planet on the stolen juggernaut ship. This was an exciting event and everyone gathered in the city square. David released the entire payload of the juggernaut and killed the entire population of the planet, including the peasants. They died a horrible death, being succumbed to the black goo. To add insult to injury, David later dissected some of their bodies for his research.
The Apocalypse Space Jockey was probably the oldest Space Jockey ever, being in a suspended state for over three billion years. While his fellows were all killed by Xenomorphs, he atteppted to outlast them by sleeping in catatonic suspension. However, he did not succeed as the Xenomorphs were still around when he was discovered by humans. He was infected by a facehugger and gave birth to the Space Jockey Alien, one of the biggest known Xenomorphs. The story of Aliens: Apocalypse is quite similar to Prometheus with Space Jockeys having ties to ancient Earth and a last surviving member of the species awakening, but being infected by a Xenomorph.
In addition to the Space Jockey seen on LV-223 in Prometheus, there was another individual on the planet in the Fire and Stone series. Set a century after the events of the movie, this Engineer encounters another group of humans and Xenomorphs. He uses awesome Engineer weapons to destroy several groups of Xenomorphs. However, his final encounter brings him face to face with a Predator, namely Ahab. He puts up a good fight against him, but the Predator gets some extra help from humans. The Space Jockey is killed by a harpoon gun and the Predator's self destruct device. Ahab extracts his head and spine as a trophy and is victorious in his hunt.
The LV-223 Space Jockey was awakened from his long cryosleep by David and Peter Weyland. Unfortunately, he was not in a good mood and not amused when David tried to communicate with him. He ripped off David's head, killed Peter Weyland and his companions. The Engineer then tried to fly his ship to Earth but was crashed into by the USCSS Prometheus, piloted by Idris Janek. Still very angry, he blamed Elizabeth Shaw for his missteps and tried to hunt her down. In the end he was facehugged and birthed the Deacon Alien.
The emissary Space Jockey was seemingly a peaceful representative of his species who both feared and hated the Xenomorphs. After the Alien invasion of Earth, he arrived on his juggernaut ship to sign a deal with Earths diplomats about the future terraforming of Earth. However, the Earths government was not interested in that and set a trap for the Space Jockey. A group of androids disguised as diplomats infiltrated his ship and a fight broke out. The Engineer was able to successfully destroy most of the androids, but he was killed when the ship was decimated by missiles from Earth. Like some of his fellow Space Jockeys, he was able to communicate telepathically, even with androids.
Most of the Life and Death comic series again takes place on LV-223 like Prometheus and the Fire and Stone series preceding it. We are introduced to a new pair of Engineers, again awaken from cryosleep on a juggernaut ship. The unmasked Space Jockey acted as a leader and the masked one more like a muscle for hire. Again, the Engineers are mostly interested in killing everyone, including humans, Predators, and Xenomorphs. One of them is killed by the Alien Queen and the other by Colonial Marines using smart guns and pulse rifles.
The sacrificial Space Jockey made an appearance in the beginning of Prometheus. He took a sip of the black goo, disintegrated and became the basis of life on a barren planet. Supposedly the planet was Earth, so he was kind of an ancestor to humanity. Although knowing that he would be killed, he was surprisingly calm and collected, so he gets extra points for it. A deleted scene also shows other priest-like Engineers watching him, possibly swaying him to perform the sacrifice.
The Space Jockeys from Alien: The Comic Book Adventure don't mess around. They had an agenda to wipe out all traces of Xenomorphs and were quite successful at it. They were even nice enough to give humans a chance to escape their death ray weapons. Looking more like space bikers, with leather clothes and black boots, their ship looks different from any of the others we see in the Alien lore. Their legs have not fused with the chair yet either. They are also one of the few Space Jockeys to survive their encounters with the Xenomorphs.
The Space Jockey from Aliens: Outbreak had the most outlandish design yet. He hovered over the ground in a space suit and was able to communicate telepathically. While his upper body resembled a classical Space Jockey, his legs seemed like horse hoofs enclosed in rubber boots. He helped a group of Colonial Marines decimate a wave of Xenomorphs with his laser weapons. The Space Jockey was able to communicate his thoughts with Billie, the main character from the Earth War Trilogy (and a name replacement for Newt). Turns out the original Space Jockey from Alien was his friend. He is one of the few Space Jockeys to not be a murdering maniac and one who actually survives.
The original Space Jockey on LV-426 from Alien is the best one. Even though Prometheus took away some of the mystery surrounding them, we still don't know where he came from and how he ended up on LV-426. What we do know is that he managed to land the ship successfully and set up a warning beacon for his fellow Space Jockeys. There has been speculation that the sequel to Alien: Covenant will finally explain the mystery, but there is no need. The original Space Jockey does not have to be David in a suit or anyone we know. Let it remain the mysterious dental patient that HR Giger originally envisioned.