At 5 hours, that would be $20 an hour if you only had one play through. double the cost per hour of a disposable bluray.
IMO if a developer says a game is between 6.5 and 8.5 then it's usually 4/5. I won't be payin full price though so it doesn't really matter as much to me.
Your right, one uses next gen GPGPU physics.
It's not just the campaign length that is in question, there is also the matter of replayability, Battlefield Campaign is 4 hours long but it is mainly a multiplayer focused game, If your buying BF4 for the single player then I'd advise that it is not a good investment on launch day.
Resogun is different again, for a start, it is much cheaper than Ryse, in fact free for PS+, Also it is a high score challenge game, Games such as do-donpachi radiant silvergun and ikaruga are also very short but the fan base play them again and again in the quest for high scores.
Ryse is focused as a single player cinematic experience, the combination of this with a short campaign is the problem, not just the length of the campaign in isolation.