Considering Halo and Gears, Respawn and Destiny - we're ok for sci-fi shooters... but if it is anything like SW Battlefront, count me in - I think Destiny looks like BF tbh.
I think sci-fi is the way to go - it takes away all restrictions like gravity, continuity with how fast stuff goes etc - you can just say yeah it's sci-fi, we have massive phallic structures that float for no reason (Halo 4), all these magic tricks? The for... err... Space dust. Why we're all sexy looking and not over 40 but then suddenly 80; non-specific scientific breakthroughs (Mass effect).
Even Skyrim has sci-fi, like the sweet rolls that can logically explain any inconsistencies with the game engine. The mammoth flew you say? You were on skooma. Add to this complete creative control when designing art, and sci-fi is king.
It's all in the game...