Let's clear some things up:
First, we have to define intelligence. It's not WHAT you know, it's HOW you're able to acquire it. The dictionary defines it as:
1.The capacity to acquire and apply knowledge.
2.The faculty of thought and reason.
Humans are "smart" not just because we know things, but how we are ABLE to know things. We can reason, question, and think for ourselves.
Second, the closest cousin to the human as far as intelligence goes is the Chimpanzee, NOT the Dolphin. Dolphins are very intelligent, but are not
equal to chimps or most great apes. Chimps are estimated to have roughly the same intelligence as a 4 year old child. They can reason out basic
problems, they can convey emotions or thoughts rudementally, and in some cases can even do things like set traps or plan for things. Coco, the female
gorilla, has a sign language vocabulary of about 1,00, words and is able to express emotion such as fear, happiness, worry, etc almost verbally
through hand signs. There's no doubt the minds of apes and chimps has alot in common with our own.
With that said, the human brain is without any doubt the most advanced of any creatures on this planet, bar none. The ability, capacity, complexity,
and useability of the human brain is not rivaled by any other creature on the earth that we know of (gotta throw that cryptozoological intrigue in

). But the simple fact is that the human brain is what has made us what we are today. Nothing else got us here (aside from opposable thumbs, which
did help). But let's be real: If you gave a chimp opposable thumbs, that would be very interesting, no doubt, but that
doesnt change the
fact that they would STILL have the brain capacity and reasoning of a 4 year old.
The human brain is every bit as much of a tool or weapon as teeth, wings, or claws. In fact, It is the most prolific, deadly, and fascinating tool on
this earth.
There are many other intelligent creatures in the world, no doubt, but to say that there are species (that we know of) that rival, or even come close
to rivaling the intelligence of mankind is false, and you're just kidding yourself.