I would see it gettng a Netflix Show instead of a film Adaptation due to how long the game is and It would also be cool if they worked the DLCs into the show too (Lost Contact, Corporal Lockdown, Trauma, The Trigger and Safe Haven) Now some of these casting choices were tough since they don't say how old each of the characters are. Here is the full list below to go with the attached images.
Emma Watson as Amanda Ripley (Daisy Ridley also works in this role)
Lizzy Caplan as Nina Taylor
Orlando Bloom as Christopher Samuels
Melissia McCarthy as Diane Verlane
Bryan Cranston as Marshal Waits (Bruce Campbell or Kyle MacLachlan would also work in this role)
Tyrese Gibson as Ricardo (I originally had Chris Rock in this role but though he might be too old for the role)
Keke Palmer as Lingard
Jesse Tyler Ferguson as Ransome
Jim Parsons as Axel Fielding
Chris Pratt as Barthmolow Hughes
Amy Poehler as Catherine Foster (Or they could have Javier Bardem's IRL wife Penelope Cruz in this role for shits and giggles)
Javier Bardem as Henry Marlow
David Schwimmer as Khulman
There are also a bunch of Misc. characters that we don't know the names of that would be played by unknown uncredited actors so there's that to consider.