it depends! the 2021 release is definitely the most visually impressive, and it or realMyst Masterpiece Edition is probably the easiest to get into. however if you want to experience the 90s cgi Vibes or want a more authentic experience, i'd recommend giving the original a try! just do keep in mind the point and click navigation can be a bit clunky, and it's easy to get disoriented in some areas (especially channelwood)... if you're planning on giving the rest of the series a try, keep in mind the sequel hasn't been remastered in 3d yet, so the original game will flow into it better (and its graphics and gameplay will be an upgrade rather than a downgrade)

you can't actually buy the original realMyst from 2000 anymore, which really sucks because it has a pretty unique look, and i've heard RM:ME is overly shiny and handles some aspects poorly. it seems to be available on the internet archive, but it might take some work to get working on a modern machine.