I don’t have to much time today so this post will be short.
My friend Adam just wrote a great post where he answer this questions: How much better do 3DS games look than DS games? Does 3DS put Nintendo ahead of Sony in the portable console wars? How does the iPhone compare to dedicated games machines?
The post compares the graphics of Nintendo DS vs Sony and vs iPhone.
You can read the Does the Nintendo 3DS Destroy iPhone & PSP Graphics? to see what portable game console has the best graphics.