Character wise I always thought Holmes & Watson had equal intelligence but used their intelligence in different ways that complimented each other.
Watson was Holmes' sounding board that kept him in check and on track.
Intelligence,
the way I understand it, is not a cover-all, all-encompassing trait for every situation. People can be intelligent in some areas and normal in others. Sorta like a specific skill in wide ranging profession.
IQ tests try to show the over-all intelligence of their test subjects.
You can exceed in one aspect of the test yet score low on another but still be classified as genius.
I think this was what Doyle was showing with the duo. Two intelligent men who combined to be more over-all intelligent than each on their own.
Films:
Sherlock Holmes (2009)
Stars: Robert Downey Jr., Jude Law, Rachel McAdams
Sherlock Holmes: A Game of Shadows (2011)
Stars: Robert Downey Jr., Jude Law, Jared Harris
Sherlock Holmes 3 (2021)
Stars: Rachel McAdams, Robert Downey Jr., Jude Law
Mr. Holmes (2015)
Stars: Ian McKellen, Laura Linney, Hiroyuki Sanada
TV Show:
Sherlock (2010)
Stars: Benedict Cumberbatch, Martin Freeman, Una Stubbs
All Sherlock Holmes Movies and Series (IMdb List)
52 titles
http://www.imdb.com/list/ls066973103/