A note on the popular "make a list of villages" idea - for the strictest criteria where the card could never be a better purchase than a treasure (or stock VP card) when playing optimally - villages can be better buys than silver or nothing.
As a corner case consider a deck where the average treasure is 2.1 coin (say hitting nothing but 6 - 10 coin for as long as mathematically possible) in a colony game. At this point, silver decreases the value of the deck, but what about nothing?
Well as noted a +2 action/ +1 card village theoretically can allow you to better time reshuffles. This is of marginal utility, but regardless is "better than nothing".
I suspect that this corner case is pretty rare (perhaps getting to plat as soon as mathematically possible and getting to colony as late as mathematically possible), but it represents a possible game state where villages are superior to silver.