The time spent on characters is why it'd arguably work better as a television series,
CrookEddy there was a thread about this
What if a 'Mass Effect' TV series were made?
Related for movie franchise thoughts
Is 'Mass Effect' "The Most Impt. Sci-Fi Universe of Our Generation
Sure it would be a costly TV series but it could be done on greenscreen like BG:Blood & Chrome.
Could all of the CGI models used in the actual Mass Effect games be converted & used within very popular CGI software Lightwave 3D for TV production?
Sure a feature film would allow more epic CGI sequences but if it is the characters that are the focus then bring back the voice actors from the game and do a TV series. But the problem is it will just feel like cutscenes of the game unless you have live ction actors recast for shooting on greenscreen.
People like to see live action not CGI characters talking when it is a real TV show or movie. No uncanny valley.
It is the idea of if you are going to be building worlds in CGI then why just do a 2 hour sci-fi-action feature film when there is a market for good space opera on TV. It is just costly TV.
BG:Blood & Chrome was supposed to be the first series but never made it past the backdoor pilot stage.
With each episode of a TV series reusing most of the CGI models the cost of making the CGI models gets spread over the cost of the series.
Sure the actual camera moves, motion capture performances still have to be created, lighting done on the CGI models, and rendered for each episode but the CGI models can be reused thus reducing the cost.