Aliens

The Aliens in The Long Journey Home.

Major Empires
There are only four of them at once in a generated universe.
 * Cueddhaest
 * Glukkt
 * Ilitza
 * Logos
 * Meorcl
 * Reeve
 * Vine Consensus
 * Wolphax

Minor Races (Stations, Ships or Individuals)
Alien races you can meet in space, or on missions.
 * %$^£
 * Cerulean Dawn
 * Dreg
 * Entrope
 * K'schar
 * Mizzurani
 * N.W.S
 * Raxact
 * Subbeq

Others
Alien races without interactions outside of quests.
 * Marritanka - insectoid race that fights in the Ilitza arena.
 * Trikiniti - sex slaves of the Ilitza with bubble skin to burst.

Non-Sapients
Races that are feral.
 * Ottakawi - Acid-spitting feral beasts fighting in the Ilitza arena.
 * Rhotan - Small beasts fighting in the arena of the Ilitza.
 * Verrakian Slaw - sentient plants that fight in the Ilitza arena.
 * Vreekitaka - Giant beast fighting in the arena against 10 Rhotan.

Historic Races
These civilizations are all but extinct, leaving behind ruins and artifacts. Based on dialogues of the Vine Consensus, they were only around after the Avulco plague, but before the Jassikan genocide, placing the Avulco as older than the Jassikan. Meanwhile the Ilitza have seen both the death of the Tchansu and the plague of the Avulco. No race aside of the Entrope and the K'schar even knows about the Charasharn, placing them solid in the realm of the earliest races.
 * Avulco
 * Charasharn - not present ingame
 * Jassikan
 * Karaphlaxi - they did not live in the Gamma Quadrant
 * Maylaa
 * Tchansu
 * Xaquindi

Based on evidence, the Maylaa are the oldest race of the Gamma Quadrant, followed by the Charasharns, then the Tchansu, then the Avulco and lastly the Jassikan. The Xaquindi aren't exactly dead, but had their prime in the era of the great galactic alliance before the Entrope helped to stop them over one galactic cycle ago. They place between the Avulco that suffered the plague three galactic cycles ago and the Jassikan which went extinct this galactic cycle.

The Karaphlaxi are from another quadrant of the galaxy than the game's setting, but died 200 cycles ago by 'accident' of the Cueddhaest. If it means 200 galactic cycles, then the Karaphlaxi might be one of the oldest civilizations that ever existed, together with the Tchansu that lived to see their own homesystem go supernova. They weren't always in the Gamma Quadrant of the Maylaa, but certainly might have been around.

Human Race
Maybe not alien to you, but certainly alien to them.
 * IASA