Battlecruiser Millennium (Gold Edition) is the latest in the Battlecruiser series, and includes a variety of improvements over Battlecruiser Millennium. List of improvements include:
50 new planetary mission zones and scenes (total of 152 regions, 238 planets, 4033 planetary mission zones)
10 additional starstations and 10 starbases (total of 96 starbases, 71 star stations)
1 new single player ACM scenario with 15 missions (advanced player only please)
20 new single player Instant Action scenarios (total of 45)
Multiplayer support (client-server model)
Mouse flight controls
Plus misc. fixes and patches
For those of you who don't know what the Battlecruiser series is about, let's say it's a fusion of all these games: Wing Commander, Elite (and Privateer), Bridge Commander, Starfleet Academy, Starfleet Command, with a few other games thrown in for seasoning.

You are basically in command of a large ship (over a dozen to choose from, ranging from cruiser to supercarrier, with a wide variety of equipment, from fighters to cloaking devices), in service of one of over a dozen different races and various factions. Would you be in service of Terran/ Galcom, Terran Insurgents, or other combinations?

Once you have your ship, you can travel among dozens of star systems, hundreds of planets and moons, and land on those that you CAN land on. Trade commodities at the various star stations (that are friendly or neutral to your faction), buy up more fuel and weapons, and perhaps upgrade your ship. Fight off enemy forces (could be raiders, insurgents, or just hostiles), give orders to marines to fight off armed intruders. Control shuttles and/or fighters (including towing, retrieval of jettisoned cargo, etc.). Capture enemy ships and send them to a star station for reward. Take control of one of the over 60 different crafts in the universe (your ship is merely one of them). Mine planets and moons for minerals (which can be sold for money). Exit the craft in first person (in space or on the ground) and fight/move in first person, including use of ground vehicles... If you can think of it, this game probably has it