I have a very simple test that can be applied in these cases:
Is the work primarily:
a) furthering emulation
b) furthering the "author's"* ego?
*i use "author" in the loosest possible sense.
Now most projects clearly come under the first category, the authors are just trying to do their best and aren't interested in themselves, Blade clearly comes under the second because AFAIK his only work in emulation is an input plugin but presumably his ego is too large to take a simple plugin release, but SupraHLE for example is in a very grey area in between, so it's not always clear.