The USB player I had at the time that the iPod came out was way easier to use. The player I had you could plug into any computer and simply copy a file.
Which is fine if you want to listen to one song. But most people prefer to listen to multiple songs.
So you've been using your media player for a while, full of music, and you decide you want to change what you're listening to. You can't just sync in a new playlist like you can on the iPod -- you wind up having to manually delete the songs you don't want in there, make sure the directory structure is correct, and then move in all of the songs you want to add.
And hope that you only ever want to organize or select songs based on album, or perhaps artist. You don't easily have the option of selecting songs off your hard drive by genre, or perhaps by decade, unless you've pre-organized your music in this manner (in which case, adding songs by album or artist is probably going to be impossible, unless you've manually maintained some huge directory full of symbolic links to organize your music along multiple vectors simultaneously). Again, doing this is ridiculously simple on the iPod, but it's a chore on media players that just present themselves as a mass-storage device. You wind up doing all the things that a computer is good at handling by hand.
And that's fine if you like that. Some people like chores. I know some people who love sweeping their floors. I'll stick to my Roomba. There are tasks that machines are simply better at than humans are, and if you like to do those things yourself, more power to you. I'm not trying to put down your choice of device, but don't fool yourself into thinking that it's easier than plug-and-play synchronization (and if you had to "go through all kinds of options to sync" an iPod, you were doing it wrong).
Again, this is one big reason why the masses flocked to the iPod. For most people, dragging music around in a UI to load up their device is boring busywork that wastes their time. The iPod only ever asked them to plug it in, wait, and go.