Backtracking is rather good as it also force you to face off a few unexpected encounters here and there even though most of the enemy surprises are cheap and highly predictable however I would say if the game allowed you to backtrack from beginning levels to the later than that's just plain absurd.
For RE1 and to an extent RE0 it's perfectly understandable to allow you to backtrack due to it's level design and setting in question but for something like RE5 or 6 I don't really see that happening much however to point out the Leon/Helena campaign in the Tall Oaks University part is just too damn short, it obviously felt like the developers wanted to offer more but inconsistently rushed to focus on later portions of the campaign.
I was just taking the preference of having the game as one big stage (allowing for backtracking and revisiting) to its logical extreme. I guess I could have also said Final Fantasy after you get the airship. I was generally speaking in the broadest sense. Of couse you can easily find fault with my analogy if you start to talk more specifically.
This is opposed to RE5 and 6 where you can't revisit places after you've finished even chapter subsections. (This obviously makes sense. It would be stupid to allow Leon and Helena to leave the Simmon's boss fight and fly back to Ivy University.)