It depends on what you're going to use the camera for. Some people's requirements are different from others.
If all you need is 1080p and half decent image quality then some of the Chinese action cameras are good value for money (SJCAM, Xiaomi, etc.).
I need 2.7K at 30fps (image stabilization, defishing, data overlay and cropping to 1080p) which rules out nearly everything Chinese so my options are the GoPro Hero 4/5 or TomTom Bandit.
Let me do a shameless plug for TomTom.
The TomTom Bandit is actually a very nice camera and rivals the GoPro range.
I even consider it a better competitor to GoPro than the Sony action camera range and may consider one depending on the official GoPro Hero 5 release specs.
The TomTom Bandit has:
- Built in GPS, barometer and accelerometers so you can overlay a map, speed, g-force, altitude, rotation (and heartbeat via bluetooth heart rate monitor).
- Bullet shape with clever battery and storage on a USB stick design.
- No stupid 64GB SD limit like the GoPro (GoPro officially only supports 64GB SD cards)
- 3 hours recording time at 1080p 30fps (GoPro sucks with battery life)
- 360 degree rotation so camera can be mounted at any angle.
- Image quality is very close to the GoPro at 2.7K resolution.
- IPX 7 splash proof out of the box. You can dive to 50 meters with it without a waterproof case by just adding a dive lens cover.
- CPL filter lens available (GoPro requires some horrible after market solutions).
- 16MP camera for stills/time lapse/burst
- Nicer mounting system IMO but one can get a GoPro adapter so you can use GoPro mounts.
Bandit review
If the best image quality or very high resolution at high frame rates are your requirements then GoPro is still the leader but no longer by much.