Hitman wasn't that linear. There was no place in SC where you could choose between two paths (backdoor or frontdoor, that kind of thing). You always had to do Exactly as the developers planned, which was kind of annoying.
I know what you mean, it was the biggest letdown of the first game. Only the CIA HQ infiltration mission had any non-linearity. But, the devs have promised "multiple entry points" for Pandora Tomorrow. How much improvement that translates into is sketchy, but it will be better for sure.