IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
Just to add to what John said, the original Wii makes a pretty good multimedia “box”, with Netflix, Amazon Instant Video, Hulu Plus, and a YouTube Channel all available, and because they are being pushed aside in favor of the Wii U, they are pretty cheap (or even better, you may have one gathering dust somewhere). You can also control YouTube through an Android smartphone or tablet, pretty much like Chromecast, although YouTube performance has been less than optimal over the past few months. It has gotten better though. The only real drawback to using the Wii is output is limited to 480p, but if you don’t mind that, it works great.
If you have a few i-Devices and just want to buy something and be done: Apple TV
If you are thinking about a Roku check into PlayOn and Plex, they greatly enhance what a Roku can do.
If you want a system that can do just about everything but requires some set up go with a HTPC running XBMC. XBMC can do amazing things if your willing to put the time in. (OTA DVR,ALL major streaming services, 1 click DVD ripping, etc)
Last but not least an Ouya. Ouya Runs android apps so you can run XBMC, Plex, Netflix, etc. with the added benefit of games.
Chromecast strikes me as fairly unimpressive.