- Earthsiege 2
- Starsiege: Tribes
- Tribes 2
- Tribes: Vengeance
For reference, Starsiege is technically "Earthsiege 3" and originally, the game was going to be called that. It was changed before release. Battledrome had very little to do with the other "Siege" games, except for the fact it involved fighting in large mechs. That game, however, took place in an organized sports-like arena.
Starsiege: Tribes was the original game in the Tribes series and used the "Starsiege" name as a way of making sure prospective buyers knew it was in the same universe as Starsiege. For the sequel, the "Starsiege" part was dropped and it was simply called Tribes 2 instead. The third game in the series did away with the numbering system and simply called itself Tribes Vengeance, which was set chronologically before the first game.
There are other games in the series (but they aren't within the Mecha or FPS genres), such as Mission Force: Cyberstorm, Cyberstorm 2, Stellar 7, Nova 9: Return of Gir Draxon, and Hunter Hunted.