Three guys have made the cutest little Metroid game you've ever seen. And if you like the cuteness they're peddling, you can go download a "tech demo" and play it yourself.
"Minitoid" is a homage to the classic Nintendo series made by programmer Tokinsom, artist Betatronic and composer Jamie Billings. It's not Metroid as you remember it on the NES; it's Metroid as you wish you remember it on the NES.
While it's of course free, remember this is a tech demo and not the full game. Also note that it's Windows-only at the moment.