I prefer PLEX for watching all my 1080p HD blu ray mkv movies (or any other video/format files) on my Surface 2 (RT). It plays everything! Ever since I started using PLEX about a year ago, I've never had to worry about converting or what video/file format a movie is in again! It doesn't matter... PLEX will convert and transcode on the fly if it cant already play it natively.
I have hundreds of movies in several folders, and I can access them all and stream them instantly to my Surface 2 in full 1080p HD!
First, download and install the free PLEX media server desktop application on your PC (I have two servers running; one on a desktop PC, and the other on a laptop) and create an account. Then, set it up by telling it which folders contain all your movie/video files. That's it! Leave everything else at default settings...
Next, get the PLEX client app(s) for $4.99 ea. (the best $4.99 you'll ever spend! I bought it for both my Surface 2 (RT) and my Nokia 1020)
Start the PLEX app, log into your account, and enjoy playing all your movies without having to worry about file formats or converting files!