Is Reiner Knizia’s Tigris & Euphrates thematic? From what I’ve seen people are split on this. I believe it is.
You are building up a civilization, having external and internal conflicts, and earning victory points in four categories. The scoring in T&E is possibly my favorite scoring system and I think it adds to the theme very well. You score points in four categories, but your final score is whichever category you have the least of. This means you must build up evenly, just like when building a civilization, it must be balanced.
I think the reason some people feel it is not thematic is its presentation. It has a rather abstract design of tiles and discs. But I don’t think that elaborate game production is necessary for a game to be thematic. The theme of T&E, building a civilization, is expressed in every mechanism of the game.
I think a game that brings across the theme in the mechanisms is more thematic than a game that has art and components that represent the theme, but lacks a mechanical representation of the theme. It’s more important to feel the theme than to see the theme.