You must have missed the
interview with Red Fly Studios during their work on the Darth Maul game where they were instructed by LFL staff not to bring up Starkiller in front of George Lucas. Kind of odd treatment for a character he considers "canon."
Besides, what George Lucas considers or doesn't consider compatible with his version of canon doesn't automatically equate to superior storytelling. Anyone who's even a remote fan of General Grievous, or prefers Korriban over "Moraband", knows this.
That was probably due to TFU 2's failure, but at the time of release, Lucasarts in general acted as if TFU was part of Lucas' personal SW universe, especially since he had such a heavy hand on its story. They originally wanted to make a Wookiee game until he vetoed that and went with the Secret Apprentice Starkiller idea.
"The new game, known by many simply as
The Force Unleashed, is the first
Star Wars game to be considered by Lucas an actual chapter in the overall story line that begins with the three prequel films--
The Phantom Menace;
Attack of the Clones; and
Revenge of the Sith--continues with this summer's animated film,
The Clone Wars and then, of course, concludes with the original three films,
Star Wars;
The Empire Strikes Back; and
Return of the Jedi."
So yeah, Lucas considered TFU to be so canon he was there when it came out and he supported the game at its release. It was G-canon at the time of its release, so overpowered Force techniques like grabbing/pulling down a Star Destroyer (which Darth Nihilus already did to the Ravager in KOTOR 2) wasn't something Lucas was against. After all, Lucas had a very positive reception to Dark Empire, and people hated Dark Empire, especially since it had OP Force powers, and yet Lucas loved that stuff, showing how OP Force Powers were approved by the ultimate authority over all of G-canon:
Tom Veitch: "We had great response. I still get letters from people telling me that
Dark Empire was the best of the continuing stories, that it should be made into a movie, that it should be a novel, etc. George Lucas told me personally that he loved it. Some people had a problem with the bringing back of the emperor. But as I have explained elsewhere, we did that under George Lucas' direction. Originally we asked him if we could bring back Darth Vader, assuming that the empire would want to perpetuate the image of Vader in order to strike fear into the hearts of billions. So they would put somebody else inside the Vader costume, of course. But George nixed that and told us we could bring back the emperor."
That second point is something I would also get at. What Lucas sees as his version of SW doesn't always mesh with the fans or prove to be what they see as the superior version. I mean, heck, I still hate the fact that Vader in ROTJ was a slave who simps for Sidious despite the fact that his son was right there, ready to help him kill the Sith master so he can seize the throne. Vader's struggle in ROTJ should have been convincing Luke that helping him to take over the Empire is the better path, instead of serving as a punching bag for Luke and a disposable towelette for Sidious. Or the fact that Lucas made Vader kill kids in EP3, when having Anakin convert them to the Dark Side would have gotten the same message across about Anakin's corruption without going so memetically overboard.
I mean, shit, if the fans had their say, Timothy Zahn, Drew Karpyshyn, and Karen Traviss would be the ones owning and running Star Wars, not George Lucas. Especially since many fans despised the Prequels and the Clone Wars movie that had Lucas' hand or support with them, while loving much of the Expanded Universe stuff that Lucas barely had a hand in, especially since the Thrawn, KOTOR, and Mandalorian stuff raked in plenty of fanboys. I still remember the last years of the pre-Disney SW era where many EU fans HATED George Lucas and wanted him to retire so that their EU author of choice can run Star Wars while Lucas sulks in the corner, ignored and forgotten. People began attributing everything good in the OT to Lawrence Kasdan, Gary Kurtz, and Richard Marquand, while saying that everything wrong with the Prequels is Lucas' fault. While I don't share their hatred of Lucas, I do understand where their viewpoints came from when it came to not liking what Lucas put in.
Although for my two cents, TFU is a better explanation for the Rebellion's rise than the Ghorman Massacre. At least the plan would have worked had Vader disposed of Starkiller, whereas Tarkin landing on a planet and killing innocent protesters causing the Rebellion to rise is the kind of Stupid Evil that makes TFU Palpatine seem downright brilliant in comparison. At least in TFU, the Rebels saw Vader and the Emperor defeated by some random Jedi figure, so they at least got inspired by seeing someone beat the shit out of Vader and give the Emperor a proper struggle, showing that the two evil overlords do have their limits. But I can also understand why people hate it because Vader acts like a tool for a bit and it gets downright M. Night Shyamalan-esque as a whole.