Man... Some harsh words here...
I'm going to have to disagree about QuickTime and RealPlayer being that bad.
Years ago, I would have agreed that RealPlayer was total crap. However, Real One has a much better interface than QuickTime, but both applications are a bit misunderstood by 99.9% or more of everyone out there.
Windows Media Player also falls into the same category as those 2 players, but it has an infinitely better user interface.
All three of those players are more than just simple "media players" - they are development platforms. There is a lot that you can do with them. I've worked with all of them, and RealPlayer and Windows Media Player in a great deal of depth. There are lacking things in there, but they are far superior to most other players.
Let me pick on myself for a bit... Take a jaunt over to view my MP3 player GDT
and look at the screen shot. It's pretty damn ugly, but it's actually very easy to use for what it is designed for. It's a special purpose player, and not meant for a broad audience like Real One, QuickTime, or WMP. (Hereafter RO, QT, WMP)
My application does what it is meant to do, and does it very well - I won the Shareware Industry Awards Foundation award for Best Application Using .Net - It has to have some merit... But, as a general purpose media player it sucks. Completely horrid.
Now, take a look at something like Foobar2000 - great for audio, but it has a wickedly miserable interface - worse than my own! But it is highly functional and a great player.
Now, try to do with Foobar2000 what you can do with WMP, RO, or QT - you can't. Those are development platforms with a very very deep level of thought put into them.
So far, I think MS has done the best job with creating something useful, but without a doubt, Apple has created the best stuff for professional applications (of the 3). Nobody uses WMP for post-production work - everyone uses QT stuff - usually with an SGI box or Final Cut or something like those. (There are a few more.)
If you're going to do any development with a media player, those 3 rock. The interfaces are very good and you can do a lot with them. That's a very important part of their interface that is not well known. If I were to choose one... hard choice. I like Real a lot for development, but WMP is ok for some things. I don't really like the interface for QT that much, but it is very good. (I'm not a fan of C based or C reliant things... Too retro for me.)
Well, I suppose you'll have to look at the SDKs for those players to know what I mean. Anyways, they aren't all that bad.