I think legally songwriting credits are given to the writer of the melody and lyrics...I might be wrong, as I can't actually remember where I read that, but if that's true then the artist is always the artist no matter how many people are involved, at least legally-speaking.
I don't listen to Kanye, so I can't really speak for this album you brought up in the OP, but it sounds like a pretty extreme example of having outside influence on an album's creative direction. Kinda reminds me of the early days of Scritti Politti in the 70s, how they'd have about a legion of people writing songs under the Scritti Politti credit, many of whom didn't actually play a note on the song they were writing.
But often I think of an artist making his/her/their album as being like a director making a movie. For all the other people you have to rely on to get things from A to B, all the people who might have ideas of their own about the project, all the external pressure that you might be under from producers, execs, members of your own band or even yourself, it's still someone's creative vision that's driving the project to completion, and as such it'll pretty much always end up as something like that initial vision (at least under ideal circumstances...doesn't always quite work like that, of course). Even if that creative vision of the individual artist involved having gazillions of producers and co-writers chip in to proceedings themselves.
...and for give the disjointed nature of the above text...hungover...bleh
