I’ve heard it theorized that if we ever contact sentient intelligent aliens from other planets, we may have no way to relate to them because their methods of thinking will be too outlandish for us. They will think in fundamentally different ways.
Nonsense, I say! While there may be some variations on thought processing speed, memory, and perceptions (being able to hear different sound frequencies, for instance, or having a stronger sense of smell, or perhaps being able to sense infrared light, though I’m not sure what good that would do), I theorize the foundations of intelligence are like the laws of physics or mathematics; they are universal. Nature always hones in on the same principles.
In this way, I believe humans are the most intelligent possible beings in the universe. If something cannot be understood by a human, then it cannot be understood by any physical being at all. There may be aliens just as intelligent as humans, but there can be no aliens with “superior” intelligence (of the “I understand things you cannot even fathom!” sort, not the “I can do math in my head faster than you!” sort), because there exist no different systems of logic that are just as valid as the system humans use, because our system is based on immutable principles ingrained in the nature of nature of itself. (I do not mean the system of logic as defined by mathematical laws in a text book; these systems are incomplete. We do not yet fully recognize the logic we use, yet we use it naturally. Its subtle simpleness and ease of use is what makes so hard to find, but we’re getting there.)