The german factory comes so late in the game, most of my marathon/large games wont see one.
Makes it near-useless to me.
On that note, the Dutch UB is extremly powerful, only if you play that far, which makes it useless to me, as i seldom see the industrial age.
Others may get more out of it, i dont.
Other than that, the Viking trading post is only really relevant at certain map types, with enough coastal cities, so it depends on your starting location as well. If you start inland, its useless to the max.
Also the greek UB is less than super to me, because by the time i get to it, i usually have enough happiness anyways, the culture in my mainland is worthless, and its too expensive to just zerg it at the borders which get courthouses first.
I highly favour the Citadel (castles give +1 trade routes, thats hard cash) it also makes trebuchets with CRIII, which, in turn, own.
Hard.
In contrast to this, the ger is probably one of the worst buildings to have.
It does not confer any more upgrades that a normal stables would (alone and with barracks) since you go either from
2 -> 4 xp (from 1 to 2 upgrades with no barracks)
or
5 -> 7 xp (2 upgrades with barracks)
in comparison with a stable.
+2 xp is nice, but another promotion would have made this useful.
The difference in combat effectiveness between a 2 and a 4 XP keshik is the same as a 5 and a 7 XP Keshik, zero.
Therefor i deem the Ger the most useless UB next to the Dun.
No, make that THE most useless, since the Dun confers a promotion instead of xp, AND is a prerequisite to castles (commerce).