Here is an utterly fantastic episode on the original Metroid from my new favorite podcast:
Listen to 057 - METROID, an episode of NEStalgia, easily on Podbay - the best podcast player on the web.
podbay.fm
And if you enjoy that, I wholeheartedly endorse subscribing and listening to every episode in order. One of those extremely rare podcasts that hits the holy trifecta of timelessness, depth, and casual hilarity. Truly the best retro games podcast I've ever come across, and it ain't even close.
But the Metroid episode in particular is excellent and gave me a completely new perspective on what an accomplishment that game was! Such an amazing franchise. Here's to hoping the rumored 2D Metroid 5 and rebooted Metroid Prime 4 finally boost this series to the heights it deserves.