Specifically about Mass Effect: I think the difficulty here is that the ME universe is pretty vanilla by scifi standards. The good part about the games is how they present a big universe and fill it up with lore and characters for you to explore and because of it (at least for me) the game's immersion goes very smoothly from "I'm playing a video game" to "I'm commander fucking Shepard and I'm saving this galaxy whether it wants to or not".

I think that'd be pretty hard to bring to a non-interactive medium. Sure good novels can be written but again, a film lacks the time to give so much exposition.