The Samsung Galaxy S8 display is the best smartphone display on the market right now. It was already tested by DisplayMate and got their approval for having the best screen they have tested to date. One of the main reasons I found the S8 screen useful for is when watching movies. Of course having a great display enhances everything you do on your phone, whether you are browsing the web, viewing photos in the image gallery, playing a game or just playing around the UI. That being said, if you are like me, you are probably spending quite some time watching movies and videos online. I found myself doing it quite a lot lately after my brother gave me the Galaxy S8 for one two week -Thanks Josh :)
Watching movies on the S8 is a completely different experience, and you are talking with a guy who has the iPhone 7. I don't know what it is, but videos looks so real. The colors just pop up, the sharpness it top-notch and you really feel like there is no screen at all, like the content itself is playing right in front of you. The Samsung Galaxy S8 Infinity display is just amazing, especially when viewing HDR content.
Obviously original uncompressed videos look the best on this display, but even watching videos on Vimeo and YouTube (Vimeo is better due to the lower compression) look stunning. The S8 was optimized for the best viewing experience and you can see that when you use it to view movies. I think that the reason that the phone is so expensive is due to its premium screen. Watching HDR content is just a wowing experience. I have a friend who has a very large LG HDR-compatible display. I don't remember the size, but I get the same quality on the Samsung Galaxy S8's display, but just in a much smaller size. Movies are very vivid in HDR, but I agree with many users that this technology still lacks content for mobile phones, and both NEtflix and Amazon Prime Video lack content for it. I think by the time the Galaxy S9 is out, many of the content distributors will offer a wide selection of HDR content for mobiles.
HDR aside, you'll still going to enjoy watching movies on this amazing display. The display isn't 16:9, but it can adjust to fit it and it's not a problem at all. Sometimes I just enjoy lying on my bed and just watch a movie with the Galaxy S8, rather than doing it in front of the computer while sitting on a chair next to my laptop computer. It's great to be able to watch videos on a plane just to pass time. Just bring your headphone, connect it to the 3.5mm headphone jack and enjoy the ride. By the way, the S8 is bundled with AKG headphones, and these headphones provide very high audio quality, compared to previous offering which were just generic headphones from Samsung.
Bottom line, superb display for watching movies, better than any other smartphone out there!