According to Wikipedia both Diamond and Archos players were DOA by 2005, two years before the iPhone was released. Creative struggled on for a few years post iPhone. 2005 was the year of the iPod Photo and the iPod Video, although the beginning of the iPod as multi-function device started in 2002 with addition of the PDA functionality.
By 2006 Apple had 72-74% of the MP3 player market, with SanDisk, Creative, Zune, Sony, Samsung, and other accounting for the remainder. I seem to recall most of the damage was done by the iPod Mini.
Correct, all those MP3 players were killed by the mini and the nano, some by the big iPod. None of them competed with the iPod Touch which was a post-iPhone product.
