Saying the Wii won't be like the PS2 is a valid enough prediction. However basing that off of Madden sales is not. The Wii demographic isn't the key target for Madden fans and most Madden enthusiasts that play every year competitively will keep sticking to the HD consoles instead of going to the Wii SKU which has a completely different control scheme they'd have to get used to.
The PS2 was dominant but not all genres thrived best there. It was the console of choice for Madden gamers last generation but shooter games still reigned supreme on Xbox. Likewise this generation even if other gamers flock to the Wii Madden will never be as popular on the Wii as it is on the HD consoles, at least not to the traditional Madden gamers you see on Madden Nation.