I don't thing achievements are, in itself, a big thing. When we made Impulse::Reactor we had achievements, matchmaking, leaderboards (which Steamworks doesn't have), mod libraries, etc. The last game that really made use of all that was, ironically, Elemental: War of Magic which was, from an Impulse::Reactor point of view, amazing (the multiplayer setup behind Elemental was beyond anything I've seen for a 4X even now and it ended up being disabled in later builds sadly because we couldn't support the infrastructure without third party usage).
With Impulse::Reactor, in Elemental, you could, from within the game, upload a mod, map, etc. to a shared library and your friends could then download and install them all within the game.
Now, getting back to more relevant discussion:
In Galactic Civilizations II we had the Metaverse:
http://metaverse.galciv2.com/index.aspx?g=map
You could see a given player's stats:
http://metaverse.galciv2.com/index.aspx?g=player&id=45
or an Empire's stats:
http://metaverse.galciv2.com/index.aspx?g=empire&id=2924
and top tournament stats:
http://metaverse.galciv2.com/index.aspx?g=topscores&m=0
And a mod library
http://library.galciv2.com/
And GalCiv II was single player.
Moreover, we could scrape this data to help the AI by finding out what technologies players researched and in what order. How they designed their ships. What improvements on what planets worked. What build orders they used, etc.
Stardock was only capable of doing this because it had the Impulse team (back then, Stardock Central but we were working on what would become Impulse::Reactor even then).
But we don't have this capability now. That went with Impulse. But with Steamworks, we can do this sort of thing again.