It all depends on how the Sony and Microsoft motion control solutions work. If Sony add an analog stick to the Arc or add a wireless nunchuck clone to go along with their remote clone then the Arc will be successful. If they don't change t5hings, it'll fail miserably. We've all seen from last years E3 that using a DS3 with the Arc looks cumbersome. And the same goes for Microsoft - they need to add a controller of some sort, again, with an analog stick.
The 360, PS3 and PC SKUs will be using the Infernal engine, most likely with the 360 as the lead platform. The Wii SKU will be 8 or 9 months away from being completed by now, meaning that it'll have an extra years worth of polish and unlike the Infernal engine, which is designed to be cross platform, is built solely for the Wii, designed from the ground up for it. This, combined with the Wii having suitable controls from the get go would have me thinking that whilst it won't be as pretty, it'll be the better SKU in terms of gameplay.