A great comic book action/adventure movie. Hard core fans might find fault with this film, but for the casual comic fan, this is a fun romp to the "other" side. The acting isn't Oscar caliber, but in movies like this, no one expects that. You want predictable Good vs. Evil and you want Good to carry the day.
The Fantastic Four delivers that without being stale and without too many wild plot devices.

any family with junior high children and older. Some of the scenes might be a little intense for the younger set, so pay attention to the PG-13 rating.

The play they gave the dynamics between the team members. This was a difficult situation mentally and they didn't skimp on the group interaction.

There aren't a lot of feel good movies out right now. This is one of them. You don't have to invest alot of energy or thought into it, it just entertains.