Well, I for one am a huge fan of the MCU, and think this movie looks very good. Why? Because I have yet to see anything to give basis to the "fact" so many people keep peddling around that "this isn't the Fantastic Four".
When the team first got their powers, they weren't immediatly transformed into the happy-go-lucky adventures everyone thinks of them as. They were scared at first, but quickly took to becoming heroes in the span of one comic, because it was the 60s and they didn't have any time for in-depth story telling. This movie is the origin of the F4, telling how they overcame viewing their powers as terrifying and coming together as a family to save the world. I have no reason to doubt that by the end of the movie they will become the F4 we all know and love.