There was mention of wanting to look for another MetroidVania game for Jeff; I think he should play Aquaria, if he hasn't already. It was available in the first Humble Indie Bundle, and is also available on Steam.
I never did get to play Metroid, so Aquaria was the first time I was exposed to that gameplay mechanic. Others have described the game as "Metroid meets Ecco the Dolphin", though I really fell in love with the art style and music, plus it also helped having listened to Oceanlab - Sirens of the Sea (the song and the album), as well as Oceanlab - Clear Blue Water (slight spoiler, but let's just say that that song came instantly to mind at one specific part of the game).
It's a rather long game for being an indie title; I think my first run through was around 14 to 16 hours, from having to find things the hard way the first time around. I played Aquaria before playing Braid (which was in the second Humble Indie Bundle), and I thought that Aquaria far outshined Braid, both in the sheer amount of content, and in the delivery of the game experience (Aquaria didn't lock the best parts of the game behind secrets).