Yes, but would it have been better off or worser off for the galaxy overall if Galen Marek killed Sidious? It would have saved alderaan and years of civil war.
Not sure it would have made much of a difference. Someone like Thrawn still would have stepped in and tried to assume the reigns. I believe Sidious also already had his clone replacements ready to go, so it wouldn't have been all said and done even had he been killed.
__________________ "Vader's pulse and breathing were machine-regulated, so they could not quicken; but something in his chest became more electric around his meetings with the Emperor; he could not say how. A feeling of fullness, of power, of dark and demon mastery -- of secret lusts, unrestrained passion, wild submission -- all these things were in Vader's heart as he neared his Emperor. These things and more."