I own every Apple TV model, Chrome Cast, Amazon Firestick and FireTV, and have Roku built-in on my 6-Series.
I place them in this order from best to worse for overall quality, design, UI, app availability, and user friendliness:
1. Apple TV 4K - Best for everything but price.
2. Roku
3. Amazon FireTV
4. Amazon Firestick
5. Chromecast - I just don't like it.
That being said, I think that ATV4k, while is by far the best of the bunch, it is overpriced and overpowered for what currently does. It could be used for so much more, and it might one day, but right now, it is an overpriced, overpowered Netflix and HBO streaming box.
If price is an issue, the Roku and Amazon devices, while not nearly as good as the ATV4K imo, are fully capable to use for the popular streaming apps. Once in the apps themselves, you will find very little difference between the streaming boxes.
I don't like Chromecast, I don't like having to "cast" everything. I like having an on screen UI and apps to pick from. I also like having a remote to use, and not having to use a computer or phone to control the device.
Apple's Siri Remote isn't for everyone and takes a little getting used to. I have been using it for over 3 years and it still drives me nuts. It is horrible for games, but you can get real controllers for the ATV to use for games.
You can also use the Remote Learning feature on the ATV and use almost any IR remote there is. I even programed my Roomba Robot's IR remote to the ATV just to see if I can. You lose some features using an IR remote like Siri, the "TV app" button, and some apps don't support it.
I have been a long time fan of the ATV, and while the ATV4 remains one of the most disappointing Apple devices ever (imo), it is still better than the competition, and Apple redeemed themselves a little bit with the ATV4K.