I wouldn't dismiss all generic feet, but a lot of them are poor quality (I've had several fall apart in my fingers), or have dimensions that are slightly out, so I have to reposition the needle just a tiny bit to avoid metal hitting metal.
The generic walking feet I have work well on all the machines I've tried them on, although they are not as well built as my genuine Janome one.
It's worth paying the extra for a genuine product, I think, especially if you are going to be using a particular foot a lot.
I believe the Emerald 116 is made by Janome for SVP, and is mechanically identical to the Sewist 525. The Emerald 118 I think is also a rebranded Janome machine, but I've no idea what model.