Please try mpv, which is basically a very good successor of mplayer, forked off the dated mplayer code.

While I do not have first hand experience with MacOS, there are multiple Mac binaries available under: http://mpv.io/installation/ - I'd start with trying the executable from Chris K, who's an active mpv developer.

plus 1 on karl's mpv

IMHO best upscale algorythm is lanczos3 implemented in kodi (former xbmc). Problem is the app is oriented as media center, so for me is only worth for LQ films.

Depending on the goal I use

mpv - 70% - easy drag an drop or multi-selection files, print screens (w/o bars and with or w/o subs); with QT, the only one that allows single frame playback, I often launch it with a script that opens as many players as needed to compare versions (the script works with any app =)
QT - 20% - with script that automatically exports stills to PS, for linear edit and mux/mix soundtrack
kodi -5% - films in low quality / screen grabs include black bars and subs though :(
MplayerX - 3% - resizable fullscreen, same screengrab (with or w/o subs) as mpv; upscale algorithm less good
vlc -2% - for any (possible) thing the others can't read