Empire of Sin
-for a serious discussion it needs titles that could be converted to mobile devices FOR REAL.
I lately played the pc/ps4 game "Empire of Sin" (an XCom inspired tbs title set in the 1920s roaring prohibition times, with Mafia & speak easy bars). This would work 100% on mobile and could become THE reference of the ever blooming genre.
...but why not go some more decades back in time?
What about Amiga classics like the Cinemaware games (Defender of the crown, It came from the desert, ...) or the excellence of grid tactics Battle Isle?
-a true blast from the past! :)