I love portraits best, so:
He seems to me the deepest painter/ portraitist that ever lived. In general, I don't find paintings to be deep - Rembrandt is the exception.
(The same applies, more strongly, for sculpture. I find good sculpture decorative rather than deep with a single exception: Rodin.)
2. 18th century British Portraitists whose names mostly begin with R
Raeburn, Ramsay, Reynolds, Romney, Gainsborough, Kneller...
I'm not sure why I like these so much, but I do!
3. John Singer Sargent
Pure joy, entrancing delight - astonishing virtuosity.