Ultimate's intensity is hard to believe for those who've not ridden it.
It's got airtime to match a good Intamin mega, more laterals than a wild mouse and positive g's so heavy, you'll struggle to remain upright. These forces are also all sustained for exceptionally long periods and all enhanced by the passing of trees at what feels like an insane speed.
It's odd, because that kind of forceful pinning you down until you hunch over, is absent on say... I305, and greying out (or whatever you want to call such loss of vision) is absent on Ultimate.
Literal intensity should surely be measured in whether or not it affects your vision (or other senses), because we know this is caused by the affect of g forces moving your blood around and so is a physical fact. I think Ultimate is more just brutal, giving the illusion of such force, by chucking you about like a rag doll.
I also think it's down to I305 building that intensity up slowly and gradually, but over a really long period of time. Where as on say Ultimate, the forces change rapidly. I also find myself getting the hunch over thing on Arrow hypers at the base of their drops, due to a rapid change from 1g up to.. whatever. On I305, your body has a chance to get used to it and keep you upright, and so the blood rushing from your head is quite a shock when it occurs.
Yes, I still love Ultimate. Even after gaining more than 100 US credits, it's staying in my top 10 I think.