Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
No. An iMac doesn't have an HDMI input which would be necessary. Even target display mode isn't possible anymore on newer iMacs.
The iMac has to run an OS then you can use a Browser or App for media consumption.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.