These aren't just any games, though. We're talking about games that include music, sound effects, and multiple layers of scrolling. These are games that work in all popular browsers, including IE, without any noticeable speed issues. (You might recall that JNES can't currently run in IE and is miserably slow even in Firefox.) If you're the kind that has to see it to believe it, try out one of their demos.
The Super Mario Bros. demo was recreated (read: not emulated) using the Effect Engine. Proof of this exists in the fact that you can move back and forward through the levels, unlike the original where you can only move forward. The Crystal Galaxy demo uses a unique mouse control scheme, which makes game play really interesting and intuitive. If you prefer shooter-style games, try out the absOrb demo, a reverse-shooter game being created by GoldCartridge.com.