The Wii, PS3 and XBox360 are all for sale next to each other in various video game stores, therefore they are in competition.
Same as upright vacuum cleaners, bagless vacuum cleaners and cylinder vacuum cleaners etc are all for sale in the same section, they might be different products in certain ways but each one is in competition to be the chosen purchase over the others.
Anyone that thinks Wii isn't in the same competition must be PS3 or Xbox 360 fans that are annoyed they are not winning
I'm sure if PS3 or Xbox 360 was the worldwide leader from the start there would have been very little talk of the Wii not being in dirct competiton from the leading console's fans, although maybe then it would be the Wii fans saying it.
It's just sour grapes.