I recently got an Android phone (switched from iPhone), so I've been trying out LOTS of music player apps over the past few days.
The one I ended up going with is Onkyo HF Player. It has a nice interface and lots of features that many other apps lack. One key feature is an "infinite-band" EQ: you can set as many EQ points as you want, at whatever frequency you want. This allows for a great level of customization, and you can equalize out imperfections in sound systems that normal equalizers can't. I didn't find this feature in any other music app. I also like that lots of features are easily-accessible from the main playback screen: lyrics, song info, EQ setting, volume level, app settings, and more. I highly recommend this music player app.
Some other good apps I found were:
- GMMP (GoneMad Music Player): very customizable and overall pretty good. However, some features are a bit of a pain to navigate to (Playlists, EQ, and lyrics), and it costs $5 (there's no free version, other than a 14-day trial)
- Pi Music Player: has a nice interface, but lack some features I want (lyrics display, and only has a 5-band EQ). If you don't need advanced features, this might be a good free player for you.
- MediaMonkey: same notes as for Pi Music Player, except that MediaMonkey is more customizable than Pi.
- Rocket Player: this one is pretty good, but the free version has lots of intrusive ads, and it's $3.49 for the paid version.
- Samsung Music: this is quite a good music app -- probably one of the better free ones. The interface is clean and it has most of the usual features you'd expect. No ads. The only reason I didn't choose it is because I like Onkyo HF Player more.
Other apps I tried, but didn't like for various reasons are: Blackplayer, DoubleTwist, foobar2000, Music Center (Sony), Music Player (I tried 3 different apps with this same name), Musicolet, Muzeex, Neutron, Poweramp, Pulsar, Shuttle, Stellio, and VLC.