I just want a media player which can play blu-ray discs, HD videos, most common formats and Ultra HD videos. Any one have a good recommendation? Thanks in advance.
First of all you should post this question under Blu ray player or media player section and not under Movies.
Buy a good Blu-ray player, it is more than capable to act as a media player too as it supports multiple formats and HDDs via USB port and also can be used as a UPnP to receive streams from your PC. Since your location says America, you can think of buying Sony BDP-S790 Blu-ray player for the same. It is 3D capable, can upscale to 4K too.
No. 1 recommendation is a PC. Plays everything and can be upgraded anytime.
Roku and WDTV are good options too.
For streaming your content WDTV is better, it handles more formats.
For streaming from internet and tons of channels Roku is better. Seeing you are from US, this is an excellent option for the price ($89 on Amazon).
But going with either is an excellent option after a PC.
Another good option is to use a PC with media server software like Plex or Kodi.
You can also consider a smart router with USB that you can use to share media, an excellent option for going 100% wireless.
Finally, a Blu-ray player but personally I'd stay from it, too many problems like region locking and Cinavia means you cannot play much of any content.
Seems to have a lot packed in, plus since you appear to be in the US you can benefit more from the streaming services.
Of course this too will not play Blu Ray discs, you would need soft copies of the rips.