BeOS and QNX (Photon) were my two favorite desktop experiences of the bunch. They were so much better than the others—yes, very much including Linux. And BeOS was even at least as "friendly" and polished as Windows was at the time.
Here we are and neither's on the desktop and their closest modern equivalent that is prevalent is probably macOS, which is... fine as a consolation prize, I guess, but I still wish I could see a world where either of those made a real splash in the desktop world (I know QNX wasn't really trying to, but man, it performed so much better as a desktop OS than Windows or Linux).