Cool, yeah the main body of those mainstream handhelds may not be "collectibles", in the sense that they are
"rare" or worth alot, but if you look those systems up on ebay, you'll see some awesome Japanese variants that never saw the light of day in any other country that are "rare" and valuable.
Take for instance the fine specimens below.
(particularly the classic, GB style Gameboy Pocket, pretty rad...)
I also stumbled upon a clear orange and clear, ice blue variant GBC, wich have me drooling and my paypal account cringing.
Oh, and for the Wonderswan fans, they also have quite a selection that surprised me, and now i'm bidding for a white, Final Fantasy Wonderswan Color bundle, wich looks pretty kick ass.
Take a gander.