Well its funny. Star Wars and Warhammer 40k are all in the Mass Effect universe too.
See, Star Wars takes place a long time ago, in a galaxy far far away. So there's no reason to see any overlap between Mass Effect and Star Wars, because the events of Star Wars have already taken place on the other side of the Universe. Ergo, they share the same universe, they just never meet or have anything to do with one-another.
Now Warhammer 40k takes place 40 thousand years in the future, maybe closer to 38, but whose counting. See with the Reapers gone, the Cycle is broken. And who here remembers their early 40k lore? During the Golden Age of Expansion, humanity traveled the stars, eradicated tons of races and created a race of AI slaves known as the Stone Men.
The Stone Men revolted and humanity was forced to destroy them in a centuries long war. Sound like something the Reapers warned us about, no?
Logically we can assume after the Reaper War, Humanity eradicated the Asari, Krogan, Turians and the others, circa 25,000 ADE. And with the Reapers gone, there's nothing to stop the Orks from coming onto the Galactic stage and fuck it, the Eldar were in self-imposed exile in the WebWay when the Reapers were about and they come back at some point. And we already know Daemons and Dark Gods exist in Mass Effect, because Dragon Age also happened. So that clears up the Warp, don't it?
Then another 20,000 years later Warhammer 40k happens.
It all makes complete sense!