VLC or MPC-HC, definitely. Newer OS', the browser has support for videos currently online, codec packs not needed. I do keep a codec pack ready to install if needed, for old/bad videos that require obsolete codecs to play.
I like all three. Each has it's purpose. MacOS for the people who would be too dangerous with anything else. Windows for business/corporate use and gaming beyond the level of webgames/clickers, etc. Linux for everything. And I do mean everything, since it is expandable to do anything, including run windows applications. Perhaps HURD if it ever comes to fruition.