PC:
Warhammer 40k Inquisitor Martyr
Console:
Valkyria Chronicles 4
Mobile:
(Warhammer 40k) Horus Heresy: Legions
Best Expansion/DLC to older stuff:
Tie between Stellaris Megacorp and Stellaris Apocalypse
Honorable Mention:
Warhammer 40k: Mechanicus
Looking forward to in 2019:
Battlefleet Gothic Armada 2
Shame of the year:
Into the breach (still not on mobile)
The disappointment of the year:
The general abandonment of mobile as a premium app platform (or the decline of being a meaningful gaming platform at all)