No one is trying to minimalize the importance of what Rosa Parks did, and what her action led to. And she has worked with civil rights since then as well. But you can't really compare her to someone like Martin Luther King who was constantly on the front lines fighting for equality. That's not to say that what she didn't end up being as monumental, but if you compare her actions to Dr. King... well, where as one is remembered for one action that got people's attention, the other is remembered for making a career out of it.
I think what she should most be remembered for is simply the remarkable power of one simple action to do something huge.