Read the Wiki article Brian linked above.
The default views in MC do not directly use the [Artist] field, so filling it in will sometimes have no effect, if the files are also tagged with an [Album Artist]. The field that is used in the default views is [Album Artist (Auto)]. This is a "calculated field" which is automatically populated using the rules explained in the wiki article. It amounts to:
1. If [Album Artist] is filled, then this "wins".
2. If [Album Artist] is blank, then the value of [Artist] is used.
There's some things fancier than this, but that's the net result that is impacting you.
So, "fixing" the [Artist] field on your files to all be Ray Charles would only work if [Album Artist] is blank. In your case, it probably isn't. Those files likely have the same values in both [Artist] and [Album Artist] (because people tag things poorly and then upload them to databases). What you probably want, is to keep [Artist] filled with the actual artists for each track, and to change [Album Artist] to be Ray Charles. That's how the system is designed, anyway. If you don't want to bother with this, you can do one of:
1. Just clear the values of [Album Artist] from those files where it gets in the way.
2. Alter the views in Media Center so that they use [Artist] directly instead of [Album Artist (Auto)] and then you can just ignore the [Album Artist] field for the future.