There is a flappy clone in c2 examples. Could you try to compile it and try to see if it works really slow as well? I personally am having a great time and constant 60 fps with a collection of around 300 sprites, some of them as large as 1000x1000, many hand crafted bone-based animations and even particles. I use cocoonjs for export to apk and get very nice results beyond s3 and newer devices. On iphone 4s and an ipad2 I have 50 stable fps, I am pretty sure somethin is wrong with either
1-) the device you are testing on (may be a very old device?)
2-) the code (maybe you are missing something and doing something every tick when you only have to do it once? maybe you are spawning thousands of objects every second? maybe you are using text objects and updating their text every frame instead of using spritefonts?)
3-)the export method (maybe you are just running on stock browser of the device instead of using intel xdk or cocoonjs to export to apk first? maybe you have disabled webgl?)
Please do not get disappointed with the product before making sure you are not skipping something. C2 is really wonderfull to use once you get to know how to use it and what you can do with it. You can be sure that you can easily make a nice flappy clone with it which runs great on %90 of the current market devices. Basically, anything newer than s3 and iphone 4. Devices before these have some problems handling html5 and games with constant movement.
Hope you figure it out.