As I play modern boardgames with greater frequency I am finding depth of theme to be important to me. For example, although I believe Terra Mystica is well-designed, the theme fails to stick for me. I'm mentally left with a set of rules to ungrounded abstractions. It feels as if the game mechanics came before the theme.
By contrast, Brass: Birmingham's theme feels very strong to me. As I plan moves I find myself thinking in terms of canals, rails, coal merchants, and so forth.
Which games do you enjoy because you find the theme immersive?