- It is all based on perspective.
- The SGC considers them false gods because they only achieved their state through knowledge.
- Everyone has the potential to ascend eventually... then they would all be gods.
- Knowledge does not equal god...
I won't touch the idea of good or evil with my answer since it is entirely possible to be both an evil or good god...
So it is basically just because of perspective. It depends on how you view the situation yourself. You see that the Ori appear to check off the boxes of what makes a being a god like creature. The SGC sees it quite differently. They see the Ori as having a greater understanding of how the universe works, simply being more knowledgeable.
From the perspective of the SGC if the only reason the Ori are 'gods' is because they have learned how to become what they are, then everyone has that ability. Therefore, everyone can be a god. i.e. Knowing more about how the universe works should not be the premise for what defines a god.
In addition, look at what the defines an ascended being. They live without a form, but can still both live and die. They know what they knew when they ascended and a little more they figured out the way, so they are still learning. They can manipulate matter (fire, make restaurants, etc.) with what they have learned and so they can do things.
These are all just heightened abilities of what a normal living being can do. Compare me to my dog. My dog can live and die, she can both know and learn things, and she can do things (lick herself, chase her tail, etc.). Now, I can do a bunch of things that she could never fathom to understanding. I [could] fly a space shuttle, throw her from a plane (in a parachute), or so many other things that seem unimaginable to her.
Just because I understand these things and she does not, does not make me a god. It means I have a greater understanding of how the universe works. The only difference between humanity and the Ori is that we have a greater understanding and so we know just how much more intelligent they are in comparison!