I started my kids on Super Mario Brothers, which we own in emulation on the Wii (the only game console I own). I’m still trying to teach my son which way to hold the Wiimote to play the game, but my daughter is pretty conversant already with the game. So I can already tell I need to practice if I want to stay ahead of them.
Super Mario HTML5 looks like a pretty good way to do that while I’m away from the Wii. The gameplay is pretty close, at least for the two levels I’ve played so far, with the exception that the sky and ground expand to fill the browser window.