I've seen everything from Predators on (except Prey, for obvious reasons) in theaters, plus Alien in its 40th anniversary re-release.
It was 2007 when I got into the franchise(s), but I (thankfully) missed out on seeing AVPR on the big screen and didn't actually see it until it was on cable a few years later.
I was born in 1994, so everything from Alien: Resurrection on released during my lifetime.