This is what i consider the best of the EU
Aliens Versus Predator ( PC 1999 )
Alien Isolation ( PS4 )
If It Bleeds
There is lots of great material but these that i have listed are, to me, the pinnacle of the EU and I hold them in the same regard that i hold the best of the movies.
Aliens: Colonial Marines
Xeno Genesis Saga
I would cheat and put AVP Requiem on the list of worst as well.
These are, for me, like really bad fan fiction. Absolute garbage. Lol i hate them.