If you already have a computer, just get a $30 ChromeCast and you can stream from Youtube, Chrome, or any files that are on your computer or on network devices you can see from your computer using a plug-in called Videostream (there are also other appearing all the time).
If you specifically want a dedicated solution, the best I have found for playing absolutely everything I can throw at it believe it or not is the old WDTV-LIVE with a custom image called WDLXTV, but generally most of the time I use a Mede8er X3D because it's easier to navigate within a particular file.
Oh, and I found the Chromecast can handle 3D content, you just tell the TV it's 3D and away you go (if you have a 3D telly that is).