Most Media players always offer something unique. I suppose the idea is to lure us to them and make us make them the media player of choice. The features they offer include support for different file formats, skins, visualizations, play lists, support for portable players, access to the Internet, media browsers, online stores and as much as Im sure i don't even know about.
For me, my media player of choice is really the Apple itunes, now this is a funny choice because it supports mp3, aac, m4a but refuses to support the wma format (Microsoft's propriety format) and must first convert wma to m4a before it can add it to its playlists. And can you blame Apple considering that the wma format was the creation of their "enemy" Microsoft who on its own took advantage of the fact that its own Media player came bundled with the Windows operating system and for years refused to support the encoding of mp3 files, a format the rest of the world was happy about, but only supported mp3 playback!
Since I own an ipod it also means that I actually need the itunes player because it is what I use to synchronise music and my play lists from itunes to my ipod.
The truth is though, sometimes it is the little attention to detail in the design of these softwares that keep us hooked. True the itunes has really cool visualizations, feels different from any other media player I know and is just "Apple cool". But can you imagine while playing with my play lists the other day I found out that settings like "repeat" and "play all" where play list specific. Thus if I set a play list to "repeat" after playing, the setting stayed with only that play list and I could set other play lists to play once for example or whatever preference I have for that play list. Imagine configuring my play lists to play exactly how I want it and the player stores those settings! Off course the next thing I did was start my Windows Media Player 11 and tried the same thing and off course Im sure you don't need a witch-doctor to know there was no such thing in WMPlayer. Not to take the spark out of Windows Media Player 11 nor to start a battle of comparisons. But for me this little attention to design detail is what makes me stick with a particular software regardless. Even if I have to use other players from time to time to play other kinds of files it might not support. True I may not always want to hear a play list the same way, but sometimes how I choose to hear the play list is an integral part of the play list too.