We have two tactics for standardising things: comparison; and referencing fundamental physics from first principles. The move towards the latter relates to the 'journey of unification' we see in the history of physics, discussed here: Is the idea that "Everything is energy" even coherent?
The meter started as the circumference of the Earth divided by 1 million; the now SI unit is related to distance light covers in a certain time, and SI unit of time to vibrations of a caesium atom. But there are other ways to define and use time, like sidereal time, years, lunar time, and timescales involved in the cosmic distance ladder. We take it for granted we can reference between these in terms of the SI scale, but the relation between these is not exact and requires intercalation, and especially at very large or small scales a fundamentally different reference may be appropriate, like the age of the universe which currently has a large error in SI terms. It is possible to run away with the idea everything is 'absolutely relative', it is not, as discussed here: The ontological logic of the relational interpretation of Quantum Mechanics And, the shift from the causal-narratives to symmetry-transformations more generally, here: Is the idea of a causal chain physical (or even scientific)?
What is intelligence? Not easily answered, because it is the kind of term about which we feel 'we know it when we see it'. We implicitly associate 'degrees of consciousness' with ability to solve problems, allowing euthenising of some humans with brain stem death, and ranking rights of different animal species, from dolphins and chimpanzees which have substantially enhanced rights to good treatment including intellectual stimulation, many rights for pet species like dogs although sentiment is a bigger factor than intelligence, to moves for better treatment of the most intelligent farm animals like pigs getting more space to raise piglets in the UK, to reduced rights for 'vermin' species even fairly intelligent ones like crows, to almost no rights for insects and shellfish. We use usually intelligence like this, comparatively.
We have many conflicting folk-intuitions about intelligence, it is meshed into different contexts or modes of life, it is part of different language-games. IQ is an attempt to replace a supposed noumena called in psychological studies 'g', with measurable phenomena ranked using IQ tests. Detailed discussion of strengths and weaknesses of this approach here: Do IQ tests measure intelligence? TLDR, the correlations between performance of individuals in different mental tasks can basically be related to health as discussed in this great paper A dynamical model of general intelligence: the positive manifold of intelligence by mutualism; but, when we look at specific examples of humans demonstrating exceptional intelligence in problem solving, we often find people like Ramanujan or Einstein who show not general intelligence and capability at life, but very unusual focus towards specific mental skills, and a better way of thinking about intelligence than IQ can help us to become a world more supportive of neurodiversity which will benefit everyone (contrary to widespread belief Einstein's IQ was never measured, because he wholeheartedly shunned that approach to thinking about intelligence).
Wisdom was considered a priority over 'cleverness' in the ancient world. I suggest wisdom is specifically the kind of problem solving that finds solutions for dilemmas, and at best reframes situations so that apparent lose-lose options can be opened to a win-win outcome. Science has seen a shift from focusing on making good decisions, to having the best modelling of phenomena, with good decisions assumed to follow. That is, solving the problems that open up the space of choices - I suggest that relates to a shift from a cultural value for wisdom, to one placing higher value on intelligence. Discussed here: Wisdom and John Vervaeke's awakening from the meaning crises?
Relating back to the 'hierarchy of being' we associate with intelligence, to be more conscious is a difficult problem for modern philosophy, because what consciousness is has been such a disputed area. Some relevant attempts at providing conceptual clarity, are the Global Workspace Theory of conscious awareness, Integrated Information Theory, OrchOR, Strange-Loops & Tangled-Hierarchies.
I see the crucial step as the shift from a local brain-led picture of consciousness in an absolute objective world, to subjectivities and world jointly emerging in an intersubjective space. Here the physics picture of what is non-comparative as related to continuous-symmetries again becomes important: the conceptual refinements and of intelligence that we call language which assemble and organise the world into salience landscapes and gives us cognitive grip on things we find meaningful, are not held privately, but gain their meaning and use from inviting each other into aspects of our subjectivities - just like with understanding Bosons and Fermions, this relates to the symmetries involved, or not, of various phenomena as we imagine ourselves into the perspective of others (science focuses on clear symmetries, psychology on fuzzier more heuristic ones). We can picture this emergence of an intersubjective space, with the metaphor Indra's Net. Discussed in more detail and related to wider philosophical thinking here: Is the Categorical Imperative Simply Bad Math? :)
There is a great picture of Ch'an Buddhist awakening, introduced in Liberating Intimacy: Enlightenment and Social Virtuosity in Ch'an Buddhism by Peter D. Hershock. Buddha's first account of what had changed after arising from the Boddhi tree was to expressly deny having become a new kind of being, but to say only 'I am awake'. Discussed here Have any thinkers applied empiricism to the dreaming and deep sleep states? and here What resemblance is there between Moksha and Nirvana? Awakening is clearly described as being 'more conscious', more present, of interacting with what is in some way more real. That very often leads to unproductive debate trying to clarify further. Hershock helps with a picture of awakening as, above all 'intersubjective virtuosity', that to diminish attachment to the conventional self opens up this capacity to see into the minds of others, and so to act for all beings. Both a fundamental sudden complete reorientation, and something that skillfulness can be attained in enacting.
I find Hofstadter's picture of strange-loops the most compelling account of minds. We create our picture of the world not as a static absolute background, but through the process of moving around a point of focus, our working memory or or Global Workspace, which processes the structures we use in different areas of life and the relationships between them, into a weltanschaung or meaning-cosmology, discussed here Which philosophers and philosophies discuss "worldview epistemologies"? This is a coherentist picture of world and minds, that minds have a quality of beginning wherever they are, and developing nested and related heurustic explanatory layers into a tangled-hierarchy collaboratively, rather than using the mathematical picture of foundationalism which inevitably is limited by Munchausen's Trilemma, and so avoiding the Halting Problem and Incompleteness that limit such approaches.
Intelligence is emergent, and by understanding it's development through enhancing intersubjectivity, we can picture a direction in which it can develop further (the rare case of exceptional intelligence in solitary species, in cephelopods, seems also rooted exactly in their ability to see into the intentions of predators and prey, see According to the major theories of concepts, where do meanings come from?).
Tegmark and Wu's AI Physicist For Unsupervised Learning, and AlphaZero point to our deepening understanding of what learning means, and pointing a direction to understanding the generalising of artificial intelligence, discussed here What is intelligence?.
AGI will emerge as a reflection of humans involved, rooted in who they are as who we are is rooted in our own ancestors. Not just what we are conscious of being, but language, culture, and all the manifestations of our attention. Rather than being children of our bodies, AGI will be children of our minds. So we should look there, to understand the future of intelligence we will make, together.
We go beyond intelligence as a comparative measure, through understanding the continuous-symmetries of intersubjectivity. We can relate this not only to intelligence and freedom-to-act, but to wisdom, and being more awake as developing skillfulness with intersubjectivity. We make our experience world in our own image:
"Watch your thoughts, they become your words
Watch your words, they become your deeds Watch your deeds, they become your habits
Watch your habits, they become your character
Watch your character, it will become your destiny."
-original source disputed, it seems to have emerged and been refined in multiple places
We will get the AGI we deserve in precisely that sense. This is not a new problem, but an archetypal one, expressed in the story of Pandora's Box, the exiling from Eden, and stealing fire from the gods - but this time it won't be us telling the story, but new beings in who's story we have only a small part.
Apologies for not being more concise.