Firstly, the ALIEN novelisation.
Then 'The Book of ALIEN'
Then the film itself.
The soundtrack LP
Then Giger's ALIEN
Then the Photo Novel
The MPC model Kit
First VHS tape I bought was ALIEN
First DVD I bought was ALIEN, upgraded to a DVD player only because of ALIEN and its deleted scenes.
Blu Ray player I bought because of Prometheus I think. (Didn't do 3D though)
Basically different presentations of ALIEN have usually instigated the move to the next best way of viewing film.
My fan adoration of ALIEN goes right back to the very start, loving the story even before I knew what anything in the film looked like. I read the book and pictured the Nostromo and the crew in a completely different way, and obviously also the alien itself. Seeing the The Book of ALIEN hooked me into the complexity of the visuals that went into making it.