A mate has the Amazon Fire TV which works great with Prime (obviously!) I tried out Prime with the 1 month free trial and while the content was good, it wasn’t user-friendly. To watch on my iPad (unless I was doing it wrong?) I had to “authorise” the content on the Amazon website (which doesn’t have a great interface) and then watch it on the iPad app. There also didn’t seem to be an easy way of watching on a non-smart TV – I did it by connecting a PC to the telly via HDMI and then watching it from the Amazon website. It works, but it’s not exactly slick.
Netflix has equivalent (but different) stuff but is a lot easier/slicker e.g. plugins for Apple TV, XBMC/Kodi, etc
For Android I just use Showbox, free and apparently legit
You honestly think it is legit when you can watch films which are still in the cinema, for free and with no ads? 🙄