In terms of speed: if you could build the exact silicon equivalent of a human brain, you may be able to run it several orders of magnitude faster, simply because it wouldn't be limited by the slow speeds of electrochemical processes in the human brain. Nerve impulses travel at speeds measured in meters per second. Neurons also need time to recharge between spike bursts, and they can physically damage themselves if they get too excited.
In terms of volume: much of our intelligence is in perceiving patterns. That's limited by cortical mass. Pattern recognition is what all these "deep learning" systems excel at. The more depth they add, the better they get. Having deeper pattern recognizers, or simply having more of them, means you can see more patterns, more complex patterns, etc. Things that might be beyond the reach of any human.
Then, in terms of data, machine have an advantage too. We're limited by our short lifetimes. How many people are expert musicians, genius mathematicians, rockstar programmers and great cooks? Very few. There's only so many hours in a day, and we only live so long. A machine could learn all those skills, and more. It could excel at everything. Speak every language, master every skill, be aware of so many more facts.
And finally, I posit that maybe we, humans, are limited in our ability to grasp complex conceptual relationships. If you think about it, the average person can fit 7-8 items in their short-term memory, in their brain's "registers", so to speak. That probably limits our ability to reason by analogy. We can go "A is to B what C is to D", but maybe more complex relationships with 50 variables and several logical connectives will seem "intuitive" to a machine that can manipulate 200 items in its short-term memory.