Alien 3
Aliens
Alien
Those 3 are my favourites and I think they are all extremely close in terms of how much I like them. I'm talking Alien 3 just about pips Aliens and Aliens beats Alien by a maggots eyelash. I hold all 3 original movies in high regard and think they're all fantastic but Alien 3 will always be my favourite one to watch.
AVP
Alien Resurrection
I think both AVP and Resurrection are ok, not bad, but not great. Could try harder. I do like them though.
AVPR
The less said the better really.
So yeah my favourite Alien movies are the original trilogy.