I didn't (and won't) vote, because I saw Gladiator too long ago and I want to rewatch it. Also, because there are at least two other movies on that list (Thelma & Louise, Hannibal, maybe The Martian) that I wanna watch at some point. But, as for now, I'd say Blade Runner > Alien > American Gangster - which I also think deserves a mention.
[Edit]
Stupidly funny fact: I've just seen that I actually voted.
I'm mostly a lurker now.