MechWarrior

You are Gideon Braver Vandenburg, heir to the planet. While you were away, unknown attackers destroyed your home, killed your entire family, and stole the Chalice that you need to win the throne. When you are implicated in your own family's death, you are forced into exile. With a help of an old friend who contributed an old Jenner and some credits, you must become a mercenary. You must travel the Inner Sphere in search of clues to who set you up, and eventually avenge your family and recover the Chalice. You have five years. Good luck and good hunting.

Mechwarrior was the first 3D BattleTech game developed. Dynamix (who later developed the Starsiege series) created it for Activision. You go to a planet and in search of "fixers" who will set up some contracts with the local authorities. The terms are a flat payment and some salvage payments. Some houses are very stingy but they tell you a lot about the mission. Others pay well but may not tell you everything. You can buy/sell/repair 'Mechs, hire/fire pilots, decide which planet to move to, as you try to maintain decent relationships with all five houses of the Inner Sphere, while trying to uncover clues about where you need to go. This ground-breaking game is very replayable, as each mission is randomly generated. There's even some extended campaigns where you run 2-3 missions in a row.

(The following is the plot from the SNES version of Mechwarrior.)

You are Herras Ragen. When you were 12 (3017) your father Colonel Joseph T. Ragen, a soldier in the House Davion army, was working to infiltrate and destroy a renegade mercenary cartel called the Dark Wing Lance and he had got in over his head. Somehow the members of the cartel got the location of your family's house on Redondo leaked to them from an unknown source. Before making their covert strike the lance made an agreement that they would separate for 10 years and maintain an absolute code of secrecy before regrouping again to continue their nefarious operations.

One night the Lance attacked your families home killing everyone inside. Over at a friend's you heard sounds of explosions. Rushing home you found a roaring inferno of what used to be the home you grew up with your family. Newly orphaned you vowed revenge on whoever had done this.

The year is 3027. Now a young man, you cannot serve House Davion after what happened all those years ago. Now you make your living working as a freelance Mercenary on the planet Galatea selling your services to anyone whose contract will lead you closer to the insidious Dark Wing Lance.