Current count is 60 odd aliens. A few youngsters among them.
Doop
Venom symbiote
Carnage Symbiote
Protector
Singularity
Alf (confirmed in Alf annual 1 as part of the marvel universe)
Star Dancer
Tiamet
Starfox
Centery
Warlock
Magus
Ravin
Lockheed
Moridun
Dreaming Celestial
Fin Fang Foom
Fifty-One from the Texas Rangers
Marrina
Longshot
Ariel
Gaia
Hyperion
Captain Britain
Psylocke
Adolp (son of the Impossible Man)
Aquarian
Blood Brother(s)
Goom
Half-Life
Kid Gladiator
Manphibian
No-Name of the Brood
Quantum
Virtue
Worm (Monsters of Evil)
Paibok
The Warbound should still be on Earth.
Magus (Technarch) was running a legit business in the last X-Factor.
Warlock (Technarch)
Karolina Dean
Warbird
Broo
S'Thalin family? - Z'nox family
Silver Surfer has been hanging around lately, since he's dating an Earth girl
Thor Girl
Darkstar is a Dire Wraith with Laynia's body and memories and powers... iirc.
Wundarr the Aquarian
[Half Aliens
Jack of Hearts (1/2 alien)
Abigail Brand is half-alien
Hulkling (1/2 alien)
Lifeguard (1/2 alien)
Slipstream (1/2 alien)
Adam X (1/2 alien)
Skarr (1/2 alien)
Ultra Girl (1/2 alien)
X-Treme (1/2 Shi'ar)]
Are there any others?