J. Alan Henning
Definitely theme. The game play of City blocks is pretty much a two player version of Kingdoms by Reiner Knizia
That's a fair comparison, in retrospect. And for those who dislike Kingdoms, I would say City Blocks is more thematic and less mathy (no multiplication). My first grader can play City Blocks and beat me but can't handle Kingdoms yet.
Though at the moment I think I prefer to describe City Blocks as "SimCity meets Suduko".