I'm still a beginner but here are my impressions after ≈25 games.
Age 1
Best : Metalworking... it's simply so fast. I really like clothing, but I find it really hard to score more than 2 cards in a single action.
Worst : Archery or Oars. Both can be good later in the game though.
Age 2
Best : Mathematics.
Worst : Currency or monotheism.
Age 3
Best : Paper (machinery being 2nd)
Worst : Feudalism
Age 4
Best : Perspective. Maybe it's just me and my playing style, but I've used it so many times for big scoring.
Worst : Enterprise. I don't get it, but reading this thread it seems like many other players disagree...
Age 5
Best : Coal. Not easy to use but so great sometimes, when by scoring you get a new great top card.
Worst : Societies
Age 6
Best : Industrialization obviously. Then... Athomic theory, Democracy and Classification I would say. There are very good cards in age 6. Democracy is great when you have a bulb lead, and you can share it in the right moment when your opponent doesn't have any card in hand. Classification is good with big hands. Athomic theory is a solid tech up card...
Worst : Encyclopedia (although it can be fantastic sometimes)
Age 7
I haven't played the age 7+ cards as much as the others, because often someone from this age the game gets faster and faster... or someone already won by achievements.
Best : Evolution or electricity
Worst : Refregiration
Age 8
Best : Quantum theory. It seems almost broken to me : three clocks (which often means free empire), draw 10 and score a 10 ? Ok you have to return two cards, but often you have useless lower-age cards in hand anyway. It was a game-decinding card more than once for me...
Worst : I don't know. Probably socialism, but I don't even remember if I already activated it once...
Age 9
Best : Satelites
Worst : ?
Age 10
Best : Internet
Worst : ?