Hi! I personally prefer the VLC player, but I recommend having at least a look into XPlayer.
The app with the bulky name "Video player for all formats - Xplayer" is a good alternative to the aforementioned video players. The ad-financed version is free and occasionally displays banners for other apps from the manufacturer - but not in running videos.
It can play almost all video and sound formats, offers pop-up playback and playlists. The interface is attractive and the file search automatically finds all media files. But what makes the app stand out among the others are the so-called "private folders". You can store videos in it that not everyone can see. They are secured by a four-digit PIN and can be restored with an email address.