I believe there was an instance, in the first or second Jedi Academy novel, where apprentices used one of the pyramids on Yavin to channel the force from all of the apprentices, through a single apprentice at the apex of the pyramid, who used that force to throw an entire Imperial fleet out of the solar system (the force of the blast even knocked all of the fleets computers, engines and sytems off line as if they were hit by a massive Ion blast). Now granted, this was in a novel and not in a game, and the apprentice at the apex of the pyramid was essentially consumed by the force (becoming one with it like Obi Wan or Yoda), but it was a massive display of the power of the force. And absolutely making the Death Star look insignificant compared to it.
There was also the time where Luke was so powerful with the force, he levitated Darth Vaders destroyed palace out of a sea, reassembled it in the air, and then set it down on a new location. He even reassembled it so it didn't have doors. He had to use the force to create an opening, and then closed it up after entering, making it virtually inacessible to anybody without his level of mastery of the force (I don't remember which novel this was from, but I remember this part of the story).
On a smaller scale, there was the time when Luke was being held in a Yuzhon Vong pain device (can't really call it a torture device since the Vong use it voluntarily

), and used the force to levitate and control two ignited light sabers, at the same time, to defeat some Vong soldiers attacking him and a companion. (Or the time Luke levitated to the surface of a planet after having an X-wing shot out from under him, and the time where Luke . . .

)
In the right hands, the Force is very strong indeed (in a fictional, this isn't real, gaming sense only - of course

).