The Mass Effect movie (anime) worked because it told the back story of one of the supporting characters in ME3 and took place in the established world of the Reapers and Collectors. That said, you probably need to have played at least ME2 if not all three to understand the context and some of the character references (Shepard, Liara etc.). You would need to find some recognisable lore or conceive a good original story given the game is set in the "real" galaxy.
Not impossible - some other game based movies such as Resident Evil and Doom have been successful but these, to some extent, relied on developing a story which doesn't necessarily mean you need to have played the game to enjoy the film or show.
Also there has been rather a glut of space based TV or late, Star Trek Discovery, The Orville etc. together with a string of cancelled titles so a studio is going to be very cautious taking on a new idea.