The 360 version will outsell the PS2 in it's opening weeks, only to be overtaken later by the PS2 version. From what I see the 360's install base buy games the quickest and tend to leave to quick drop offs. Look at GHII, the PS2 version has been out longer, but it's outselling the 360 version in weekly sales again. Also, on the hardware front, the PS2 sells more than the 360 in the US, so it's install base is still growing faster than the 360, despite being so damn old. It's likely that a decent ammount of those might be people rebuying the system because it broke or whatever, but the PS2 still has a lot of steam in the US.
The Wii version will do really well in the long run. Look at how well PGA Tour 07 did despite being a late port with no
additions besides the controls and sub-par graphics. EA isn't specfically advertising the Wii version, so a lot of it's sales will probably could from word of mouth, which will mean gradual sales over a long period of time. It has online this time, better refined controls, exclusive features, touched up graphics, and it's cheaper than the HD versions. I'd guess it might come up a little shy of a million by the time 09 comes out.
PS3 version will defintely sell the least. Smallest install base, 360's version has a better frame rate, Wii versions has
the controls and exclusive features. The only people who will buy it are likely to be people who only own a PS3, which since it's the small install base, isn't a lot. You'll see big sales the first week, and a sharp drop-off the next.
Graphics/HD arguement really only to apply to multi-system owners. Madden is on everything (it has to be) so I
doubt anyone will be buying a system for Madden, unless they don't already on a video game console, and even then
I doubt Madden will be the reason someone chooses one system over another.