I loved Halo Wars! I used to play it senseless for a while, it's not amazing, but pretty fun. Loved how it portrayed a lot of lore and elements of the Halo Universe in RTS fashion (ODST drops and Scarabs, yeeeeeah!) I lost my copy unfortunately ): Hope the sequel is both on One and PC.
Oh AND give us the ability to play as The Flood and/or Forerunners-Tech!