The other game we've been playing a lot of lately this past year is Viticulture for that same reason. Complex enough to scratch the itch, but doesn't draw itself out for way too long.
Viticulture is a good one. But IMO, the Tuscany expansion board is immeasurably superior to the original, and I prefer to play with the Rhine Valley cards to tamp down the effect of the many BS cards in the base set. I find that combination does the best job of focusing on the core mechanics.