Yes, this is a relative and variable question for everyone. Which are the best Olympus cameras ever made? Peter Forsgård published a video review and made a list of the best Olympus cameras ever made.
By the way BCN+R has published sales numbers of interchangeable lens mirrorless cameras sold in Japan in 2020. OIympus E-M10 Mark III beat out the rivals and win the no #1 of mirrorless cameras.
See also : Best Lenses for Olympus E-M1 Mark III and Best Memory Cards for Olympus E-M1 Mark III.
Also join the Micro Four Thirds Users Facebook Group to share your Olympus photography.
For me it has to be the OM1, just a game changer and still a delight to hold and use
I had and used every one of the 35 series but my favourite is the 35RD as it was smaller than the SP and had a GN lens to couple the aperture with focus distance for flash.
I still have film in my OM4Ti and XA
The E500 had a great sensor. My favourite PEN is the EP5
I still keep the EM1 mk1 for studio work.
I have had use of all the brands of cameras over the years and while they are all “mostly” good, the Olympus are excellent cameras that meet all my requirements