The most logical devices to compare with the Amazon Fire Phone are the Apple iPhone 5s, the Samsung Galaxy S5 and the Google Nexus 5.
At 1280 by 720 pixels with 315 pixels per inch (ppi), the Amazon Fire Phone's display resolution is a little lower than Samsung Galaxy S5's 1920 by 1080 pixel resolution FHD Super AMOLED HD display with 432 ppi, or Google Nexus 5's 1920 by 1080 full HD IPS display with 445 ppi. It's a little closer to iPhone 5s's 1136 by 640 pixel resolution Retina display with 326 ppi. The Fire rests in the middle as far as screen size at 4.7 inches (11.9 centimeters), compared to iPhone's 4 inches (10.2 centimeters), Nexus 5's 4.95 inches (12.6 centimeters) and Galaxy S5's 5.1 inches (12.9 centimeters).
Similarly, the Fire's rear-facing camera, at 13 megapixels, is technically better than iPhone 5s's and Google Nexus 5's 8 megapixels and technically worse than Galaxy S5's 16 megapixels. But picture quality involves other factors like the lens and the software and the lighting, so it's hard to say whether one is really better than the others at this point. However, while all of them can shoot 1080p resolution video, Galaxy S5 is the only one that can do so at 60 frames per second (fps) -- the rest do 30fps -- and the only one that can shoot much higher resolution 4K video. The front-facing cameras are 2 megapixels for Galaxy S5, 1.3 megapixels for the Nexus 5 and 1.2 megapixels for iPhone 5s, compared to Fire Phone's 2.1 megapixels.
The Samsung Galaxy S5 is running Qualcomm's faster quad-core Snapdragon 801 CPU with speed of 2.5 GHz, while Fire Phone is running the slightly slower Snapdragon 800 at 2.2 GHz. The Google Nexus 5 is also running on a Qualcomm Snapdragon 800 CPU with a speed of 2.26 GHz. The iPhone 5s runs on Apple's customized Apple A7 processor, so it's a little more difficult to compare. iPhone does run with only 1GB of RAM, while the others all have 2GB RAM.
iPhone runs on Apple's proprietary iOS operating system, whereas the others run versions of the Android operating system. The Samsung Galaxy S5 and the Google Nexus 5 run Android version 4.4 KitKat. Fire's OS is a more customized version of Android. The Galaxy S5 and Nexus 5 will likely be compatible with more apps in the Google Play store since they are running fairly standard Android versions. For apps, iPhone has the Apple App Store, and Fire Phone has the Amazon Appstore. Amazon's Appstore has around 240,000 apps, whereas Apple's App Store and Google Play have over 1 million each.
The Galaxy S5 also has a slightly heftier 2,800 milliampere-hours (mAh) battery compared to Fire Phone's 2,400mAh, Google Nexus 5's 2,300mAh and iPhone 5s's 1,570mAh batteries.
iPhone has WiFi 802.11a/b/g/n, while the others also add ac to that. All four support Bluetooth connectivity, but the Fire uses Bluetooth 3.0 while all others use 4.0, so Fire Phone might not be entirely compatible with all your wearable devices until that functionality is upgraded. The Galaxy, Nexus and Fire all support NFC while iPhone still does not.
Fire Phone, Galaxy S5 and iPhone 5s are all nearly the same price (with some variations in available storage space). Google Nexus 5 is available in 16GB for $349 or 32GB for $399 without a cellular plan, and $99 with a 2-year contract with Sprint at the time of this writing, making it the cheapest choice. Amazon Fire Phone is currently available for AT&T only, while all the others are available for multiple cellular carriers.