According to CBR Shuri is ‘the Smartest Person in the World’ in the Marvel Cinematic Universe. But in comic books or several lists of "Smartest Marvel Characters", she is not even mentioned.
The character of Shuri that was introduced into Black Panther may share the name of T'Challa's younger sister from the comics, but otherwise she is a completely different character.
The Wakandans Princess Shuri in the mainline comics continuity is a warrior, and in fact is being trained by T'Challa to become the next Black Panther in the event of his death. She's also involved in Wakandan politics (especially when her mother dies and she becomes Queen, at least until T'Challa decides to marry). But she is never shown to be particularly involved in science, research, or technology.
The character in the MCU universe, on the other hand, has been explicitly stated to be the smartest character in the MCU, at least by the Black Panther's producer Nate Moore:
As far as the technologically-advanced side, in our mind, and in our incarnation, Shuri is the head of the Wakanda Design Group. She’s the smartest person in the world, smarter than Tony Stark but she’s a sixteen-year-old girl which we thought was really interesting. src
Now, that's just one producer of one movie making that claim, and not anyone from the Marvel creative team (e.g. Feige) with broader reach, but it's pretty unusual for Marvel to let someone make that kind of outright statement of fact if there's not at least something to support it.
Everyone has different excuses for why Shuri is the smartest but no one sees Tony's creations:
- A new element in Iron Man 2
- The arc reactor with nearly infinite pure energy
- The Iron Man armour strong enough to defeat the Hulk
He is also able to stand toe to toe with Thor, has multiple PhDs in Mathematics and Physics, made his first Iron Man suit in a cave with few resources, graduated MIT at the age of seventeen (not even Shuri was able to do that) and his intelligence was even admitted by Thanos in Avengers: Infinity War.