For the scope of this question, let's consider an intelligent system as something with the properties of accomplishing some kind of goal(s). By this definition, all people are technically intelligent systems somehow, one could say (what defines a "goal" and to what extent is it actually "accomplished" is tough).
But speaking more typically here, people would more so associate "intelligent system" with something like a machine; something not biological and without "consciousness" because the word "system" may conditionally drive people to think of a "systematic approach" as "non-human" because something "power-driven" may imply mechanical, despite the fact that people are "power-driven" as well (energy).
Consider the latter though. A tool is usually built for a purpose, or a set of purposes. An example is the "smartphone". Smartphones are believed to be "smarter" because they enable you to do more computing tasks like you would on a desktop, multi-purpose machine with multi-purpose software and systems, available tasks, and possibilities to use/build these tasks. This is, however, implying that the desktop computer of 'X' architecture with 'Y' design is "smarter" than previous generation cellphones.
Knowing that the whole scope of computers, including software and hardware, is wide and this will get off-topic by having me explain everything in greater detail, so that's to be avoided. In effect, the "common computer" is generally considered intelligent today because it was made to be more efficient, multifaceted, user-friendly, and having a massive scope of possibilities to do a massive array of things.
A can opener is "stupid" because it can only open cans. Then again, is a computer really smart, or is it just set up to make you think it's smarter from your interaction and interface with it today?
Those "cool looking" smartphones seem smarter everyday, but relatively little to nothing changes on the lowest-scale of its operation: logic gates, a power source, and engineering design of electrical flow, among other related components, which allow you interaction, memory, processing, and display.
A smartphone isn't necessarily getting smarter; it's more so tricking people into thinking it is from their level of interaction with it. The system is still, on the lowest-scale, like any other computing algorithm, regardless of design, to process data/instructions and give output from input, and related functions.
If we consider the Turing-complete algorithm and set of rules for computing at its level of operation of its foundation of design, a smartphone is actually no smarter than a 1960s mega-box punch card machine.
Just because you can run so much "cooler" stuff on your smartphone doesn't necessarily make it smarter. People, like machines, can be considered intelligent machines.
What is the relation between an intelligent system in a machine and an intelligent system in a human?
Can we simply say that machines are smarter than us? Are we biased and selfish by assuming we are smarter and more capable than a modern computing device of any kind? Are we both smart?