Campaign lengths

[AlkamistStar]

It all depends, like Barozi said, the difficulty definitely ramps up the hours.

For an FPS, I find 7-10 hours ideal for a single player campaign on average difficulty. Max difficulty hourly range of 9-15 would be great. I think the Halo franchise accomplishes this, as well as the COD series. The mulitiplayer is the bread and butter though.