It doesn't have to, there are enough high caliber games coming around its launch that it just adds to the reasons why one would pick up a WiiU. Its not a starter, but its a great bench player. Its supposed to be releasing in October if I recall, meaning it'll have help from Wonderful 101 and Pikmin 3 still, as well as Arkham Origins and Splinter Cell. It'll be a good second half for the Wii U with titles like these all being available so close together.

Splinterell and Batman definitely will do nthing for Wii U. Sonic will help more.

Why has every game to be a system seller. Important is that Wii U grows a library worth considering a purchase. And Sonic helps it. Like every game.

yes it will be "a" system seller.

say it for Game & Wario

I think it could. Platformers and Nintendo always go together well

Yes, if Lost World (or some other Wii U-exclusive core Sonic platformer) turned out to be that good I would very seriously consider a Wii U purchase, but I wouldn't pick it up for a few years until I could get the console at a cheap price (probably $200 or less).  Same goes with the PS4 and any exclusives I might be interested on that platform.  Picking up the Xbox One sometime next year is my first priority, as that is where I expect I will play most of the games I want to play over the course of the next generation (and I fully expect to see some Sonic games for the X1 in the future).

Different people are interested in different games....

Probably not. Not because of the game in itself, but because it will be overshadowed by the Mario, DK and the likes. The Olympics game might move some units though...

I suppose it's worth asking at this point; how many console sales does a game need to be responsible for to qualify as a "system seller?"