VLC has been versatile, reliable, and available across platforms for a long time now. I use it for the simplicity of having a familiar and ready solution.
On windows, I have been a big fan of MPC-BE for years. That being said, I switch to linux (arch BTW) and now I watch basically everything using jellyfin instead.
That being said, VLC is the main Linux option, so VLC I guess.
In recent years I would have to say MPC-HC simply because it plays everything I throw at it flawlessly while VLC has failed me more and more in recent years.
mpv is better than either imo. Was a long time vlc user who switched this past year. It's highly customizable with a bevy of support documentation, has an incredibly clean ui, and most importantly, it just works flawlessly. I highly recommend it