What makes the best media player on Android?

Just to want to find a media player on Android to do the all the task. I counldn't help but wonder what makes the best media player?

Here I will name some points.

Play all kind of formats. 
Many people will turn to a Video Converter for help. But I don't want to waste so much time on a little 3-minute video. So, please, let me play the popular formats, like avi, flv, mkv, mov, mp3, and so on. Don't  ask me to download any codecs.

Watch Online Videos
I know there are YouTube for Android, Vevo for Android, Discovery on Android. However, I want them in a single app. So I don't need to switch the apps back and forth. I can stick to one app and have them all.

Maybe Download Videos to Android
There are many online youtube downloader. However, I just want to download youtube video directly on Android.

Tell me what is hot here
Give me some hints or recommendations about what are the most popular videos there. So I can catch the trend.

So what is the best media player on Android? You may leave some comments there.