Not sure you have room but -
As a LAST resort, I have in the past taken a hammer and screwdriver and pounded the screwdriver completely through a filter so it sticks out both sides. You then can grab the screwdriver and twist it to loosen the filter. As you might expect, it makes a big mess. You will want to insert the screwdriver nearer the genny as opposed to the end of the filter.
* Or you could drill holes on both sides and then insert a screwdriver.
And no disrespect intended, but make sure you're twisting in the correct direction.