If you have the Playstation 2 definitely consider getting Encounters, Bethesda made two games, Encounters and later Conquest.
Conquest is more limited in what it allows the player to do and the ships available. Its more like Birth of the Federation I suppose. The player can only select one empire at a time, complete a small number of similar missions and has 6 ships to a race.
Encounters covers many eras, the player progressing through them as they complete the "episodes" of each. It also has many more ships and the missions have a good variety to them. Theres also the skirmish mode which has several options, I tend to keep playing the "onslaught" mode.