Uniwar is the best asynchronous game in my opinion.
There's also Neptune's Pride (web browser game), which can both be played in real time or turn based asynchronously, and is the best strategic/diplomacy gale there can be. From Iron Helmet Games, also Buccaneers, Bounty and Boom!
In the world of boardgames, I suggest to the people who like Star Realms to try EPIC (from the same creators) which is amazing. Still in alpha but already working fine with an active community.
I would also add Diplicity (adapation of the boardgame Diplomacy), Ascension, and Twilight Struggle.