I've got a big universe... And I will die on this hill, they are canon! MCU ain't got shit on this!

Predator 2 features a xenomorph skull. So even before the AvP movies, these two alien species were in the same universe.

Spaceballs features a xenomorph jumping out of John Hurt ("Oh no! Not again!"). This happens in a diner near the end of the movie, and Lone Star's Winnebago is parked outside, next to the Millennium Falcon. So Star Wars is connected.

Star Wars prequels feature ET creatures in the senate. And ET seems to recognize Yoda (Halloween costume) while walking on the street.

Going back to Aliens, the marines use a USMC Smartgun. In Soldier, Todd's certifications include this weapon. So they exist in the same universe. Soldier also features a spinner from Blade Runner in the junk on the planet. The writer David Webb Peoples confirmed that the films exist in the same universe. I believe Todd's combat history include references to the Shoulder of Orion and Tanhauser Gate, which Roy mentions before he dies.

Todd's history also connects to Star Trek, with references to the Nibian Moons, Antares Maelstrom War and War of Perdition's Flames. So that captures Star Trek.

If you want to start stretching it further, Todd was also credited with Plisken Patch, O'Neil Ring Award, Captain Ron Trophy, Macready Cross, Cash Medal of Honour, and the McCaffrey Fire Award. If you squint through this, then technically you could consider those Kurt Russell movies to be canon. Squinting a bit further, the SG-1 shows are considered canon from the Stargate film, so now you're getting into TV.

So Predator, Aliens, Spaceballs, ET, Blade Runner, Star Wars, Star Trek, Stargate, Soldier - and maybe even a bunch of Kurt Russell's filmography - all exist in the same universe.