I've been playing a lot of economic games lately, Capitalism, Imperialism 2, being a trade empire in Europa Universalis 3...and I've found it all extremely lacking in that something that I am interested in.
I used to play Space Merchant, a game that is now Space Merchant Empires...it was fun, but now there are too few players for me to be interested in it. The best part was moving stuff from trade station to trade station, being able to take over and build stuff on planets, and constantly improving your ship and stuff.
There simply isn't a single player game that recreates this gameplay. X3 Terran Conflict comes close, but it is not a very well optimized game, and lags badly on my systems (including my desktop which is not so far behind current gen as to not be able to run that kind of game. There are games like Port Royale 2, which at least allows you to own businesses in addition ot being a dynamic trading game...
Oh well, I will keep looking. I'd like to be a single player in a dynamic world. Basically all the fun of the multiplayer games but able to do so without an internet connection, or dealing with people wanting to be complete assholes.