More important or more importantly

Which is the right usage in the context mentioned below?
Statement 1. Statement 2. More importantly, statement 3. or
Statement 1. Statement 2. More important, statement 3.

This question really needs more context.

I think “more important” uses in case you are making comparison. And, “more importantly” is about to make emphasizing/stressing/pressing.
Ex: It is more important than …
I love my girl friend because of her kindness and, more importantly, sincerity.

While some tools exist for assessing software usability, they typically are proprietary. More importantly, they do not do a good job of assessing usability across domains.
I would like to know, whether we can replace “more importantly” with “more important” in the said sentence?
If so, does it make any change to the meaning of the sentence?