Actually I think they are two different endings. The first if you go light side and the generator is activated, the second if you go dark side and it isn't.
As for the Star Wars is not about darkness, I can only think Yminale hasn't watched the same movies I have. It may not be about it, but there is plenty there.
Sure it's melodrama, and the bad buys are really bad, and the good guys pretty good, and the god guy win in the end. Emphasis though is definitely on "in the end".
On the way pretty much the entire Jedi order are first weakened, then hunted down and killed. A big, destructive civil war, the people of Naboo are rounded up into concentration camps and entire planet blown up. I guess if you find religious purges and genocide light hearted it's all a giggle.
Not to mention Qui-Gon getting killed, we know Pademe dies though maybe not on screen. Anakin's mother gets tortured to death, Leia and Han are both tortured, Luke has his hand cut off.
Is that not dark? There isn't lots of blood everywhere, but then there wouldn't be in game either.