Star Wars is almost forty years old, and a lot has happened in four decades. The franchise has expanded with its "Extended Universe" fiction, ret-conned itself around plot points in the prequel trilogy, and is now preparing for another journey into a galaxy far, far away this winter. Though Disney has essentially killed off the Expanded Universe to make room for its new trilogy, video games have played a major role in creating a vast playground of Star Wars fiction.
TIE Fighter (1994)
Though X-Wing was the first to simulate Star Wars space combat, TIE Fighter has arguably captured much more attention and enjoyed more longevity. Its refined mechanics certainly helped, and the progression lets you see the full journey from blaster-fodder in a shieldless standard TIE Fighter to a much more capable pilot manning some of the best prototypes the Empire has to offer.
More importantly, it was one of the earliest explorations of the Empire's side of the conflict. Long before George Lucas decided the Empire was crawling with clones, TIE Fighter let us see how signing up for the Imperial Navy might seem perfectly reasonable for a citizen of the Empire--until Palpatine brands you with Force Lightning, at least. At that point you have to imagine your pilot would start to question if the side being ruled by a dark wizard with a monster face is really the noble one.
Biggest Contribution: TIE Advanced and TIE Defender models. Though Vader was shown piloting his own custom Advanced X1 model, TIE Fighter established it as its own model in the fleet, alongside the Defender which was less reliant on Imperial docking due to its own hyperdrive.
Star Wars: Shadows of the Empire (1996)
Part of a multimedia push that included a novel, toy lines, comics, and other merch, Shadows of the Empire brought in a whole new cast of characters and filled some gaps left by the original trilogy. Set between Empire Strikes Back and Return of the Jedi, players were introduced to Dash Rendar, a kind of Han-Solo-redux complete with his own ship that bore a passing resemblance to the famed Millenium Falcon. He even had a sidekick, a droid named Leebo.
The novel focused much more on the main characters from the series, particularly Leia's interactions with the crime boss Prince Xizor. The video game was all Dash all the time, though it did treat Xizor with the appropriate level of cartoon supervillainy. There was a lot to this game, something we went into greater detail about earlier today.
Biggest Contribution: Who doesn't love having a second Han Solo around? As a multimedia whole, Shadows of the Empire's most important addition was of the Falleen race in general, and Prince Xizor in particular. Several novels since have made use of him, either in person as a character or in passing as mention of a dangerous criminal, while the Falleen's contrived pheremone powers have come into play elsewhere as well.
Star Wars: Knights of the Old Republic (2003)
Still revered as one of the best Star Wars games of all time, Knights of the Old Republic took Dungeons & Dragons RPG mechanics and applied them to an original Star Wars story. KotOR was one of the first stories to set itself thousands of years before even the prequel trilogy, and several other pieces of Expanded Universe fiction drew inspiration from it and built their stories around it.
On top of its story hooks, it delivered a living, breathing universe, with worlds both borrowed directly from the films and crafted whole-cloth, characters who felt at home in the franchise, and the wish fulfillment that can only come from letting you live out your journey as a Jedi. There's a reason fans clamored for years for a new Star Wars game from BioWare, and this was it. The Old Republic builds on the foundation here, but it wasn't nearly as revolutionary.
Biggest Contribution: The Sith Wars era owes almost its entire identity to the story beats BioWare established here, along with notable characters like Darth Revan.
Star Wars: Republic Commando (2005)
Proving that the prequel trilogy can fuel some great expanded fiction, Republic Commando posited that Clonetroopers could still have unique personalities. It featured Delta Squad, an elite group of four commandos in the midst of the Clone Wars. The story from there becomes a hardened military tale of loss in battle, as the Clonetroopers are used as pawns in several influential battles fo the Clone Wars era.
As a stab at the then-popular squad-based first-person shooter, it was fairly well-regarded in its day, and the popularity of the characters has only made it more so in the intervening years.
Biggest Contribution: Delta Squad went on to be featured in a series of novels, along with appearances on the Clone Wars cartoon. Plus, the notion of clones as interesting individuals has been reused many times over in lots of prequel material.
Star Wars: The Force Unleashed (2008)
After Mara Jade gained popularity as a former hidden assassin working for the Emperor, LucasArts decided: why couldn't Vader have had his own secret apprentice? After all, Sith make such a habit of betrayal that it's almost ritualistic, a sort of Darwin's Law that weeds out the weak by having them killed by their apprentice or, otherwise, by a Master smart enough to see when it's coming. Enter Starkiller, an orphan-turned-assassin trained for the explicit purpose of killing the Emperor so that Vader himself could take the top spot in the Imperial pecking order.
The story was an alternate universe, ultimately letting the player choose whether to kill the Emperor or Vader. Neither one remained in place as canon, for obvious reasons. As a what-if story, it helped showcase the greed and deception at the heart of Sith relationships. Plus, it used a wide combination of physics engines that let you toss around Stormtroopers like toys, so it was an enjoyable playground if nothing else.
Biggest Contribution: LucasArts finally found a use for the hokey "Starkiller" name found in early drafts of Lucas' scripts, for one thing. While its central conceit prevented it from being an accepted part of Star Wars lore, it opened the door for an alternate universe--which, given that the EU in general is all one big alternate universe now, isn't all that unheard of.
Honorable Mention: Star Wars: Masters of Teras Kasi
Biggest Contribution: Testing the limits of Star Wars fans' patience, in preparation for the prequel trilogy.
Steve Watts posted a new article, 5 Games That Expanded the Star Wars Universe
Star Wars Rebellion actually included a ton of EU content in it, so I might put it out there before Force Unleashed for that type of thing.
Rebellion also made way for Empire at War, one of the greatest Star Wars games according to the shacklisticle.
Didn't some of the force powers that later made their way into the universe come from the Jedi Knight games?
No mention of Grand Admiral Thrawn?
Yep, you hit all the marks with this article. Thank you for mentioning Tie Fighter first, as is it still is the greatest game of all time for any system to me.