It may sound Weird to you, but yes, they don't display the same names in GMail, Google+ and Orkut.
The name Displayed in GMail and Google Talk will always be the same.
This is a Screenshot of one of my Contact Details in my GMail account:
You can change their name in your Google Contacts - this change will reflect on your Google Contact List, GMail Integrated Chat, Google Talk and e-mails you receive from the particular individual.
But you cannot change their name in Google+ Profile, it's completely their choice - this will be reflected in their Google+ Profiles, Google+ integrated chat and hangouts, notification e-mails you receive through Google+ related to the particular individual.
The same applies for Orkut (not that anybody cares about it).