Roku is my favorite. I've been using a Roku box for several years now. I'm not even sure which generation it is as they seem to have changed the remotes. It's a great device with easy setup and a lot of channel options, including: Netflix, Hulu Plus, Amazon, Google Play. There are a wide variety of other channels free and paid. Roku does seem to cover most of the options. There are currently 4 versions of the Roku box available from the Roku website ranging in price from $39.99 for the Roku LT to $99.99 for the Roku 3. They also offer a Streaming Stick for $39.99. The website claims the stick is best for wall mounted TVs. It's also very portable so you could easily take it with you when you travel or move it from one TV to another in your house. There are Roku apps available for smart phones and tablets so you can control your Roku either with a remote or with the app.
Roku also seems to have gotten into the Smart TV business recently. They now have that option on their website. I don't know anything about the quality of the sets but the prices seem good. $598 for a 55 inch Smart LED TV from Amazon. I would imagine it's easier to set up than many smart TVs as it's Roku. But I happen to be a fan of separating functions.
Compare Roku Players
Google Chromecast website
Amazon Fire TV
Amazon also offers the Fire TV stick for $39. The remote app allows you to use voice search on the Fire TV stick as well.
Amazon Fire TV on Amazon
Apple TV on Apple website
Roku vs. Apple TV vs. Chromecast vs. Amazon Fire TV: Which streamer should you buy? - CNET Review