Just like a gaming PC, a Mac is not an all-in-one solution. A gaming PC plays games great but is so-so in some other production applications. The Mac is the opposite.
That being said it would be great if a GeForce card was standard.
If we're talking movie production, the gaming PC wins. If we're talking 3D production, the gaming PC wins. If we're talking connections, the gaming PC wins. If we're talking word processing, it's a tie.
Just which "production applications" is an iMac better at than a machine you can buy from Alienware or Dell or Rock or somewhere else right now for the same money?