So far, two former Star Trek cast members have lent their voice talents to the first two games, both from Star Trek: The Next Generation; Marina Sirtis (Troi) as Matriarch Benezia in ME1, and Michael Dorn (Worf) as Gatatog Uvenk in ME2. Assuming the trend continues for the final game, which former Trekkies in your opinion should be included in ME3?
Personally I see roughly 5 potential choices for a role in the game: William Shatner (Kirk), Patrick Stewart (Picard), Jonathan Frakes (Riker), Jeri Ryan (Seven), and Robert Picardo (Doctor).
Picardo and Stewart would have the upper hand as they've already done some voiceover work: the former voiced a few roles including Amazo in Justice League and JLU, while the latter has done at least one known role; as Pharaoh Seti I of Egypt in The Prince of Egypt. Both of them are known as powerful speakers.