I'm really not sure what you're referring to here. Do you mean you're never getting great people? Is the GPP bar full? You generally get fewer great people later in the game as each one costs more.
I may be misunderstanding you, but you seem to be under the impression that a wonder automatically gives you a great person. They don't, each wonder gives great person points, and once the bar is full a great person will appear. Each great person requires more points than the last.
By adding them in manually I presume you mean you are cheating with world builder. This is a very pointless activity.