The first two are definitely awesome, but the new revised version with different actors is kinda meh.
The very first Fantastic Four (2005) stars Chris Evans (Captain America ) as Johnny Storm/The Human Torch, Jessica Alba as Susan Storm/Invisible Woman, Michael Chiklis as Ben Grimm/The Thing and Ioan Gruffudd as Reed Richards/Mr. Fantastic. It's rated PG-13, and it is REALLY good.
Fantastic Four: Rise of the Silver Surfer is actually rated PG (that is very surprising, LOL), and it's also really good. Lawrence Fishburne is the Silver Surfer.
The new one, though... Eh, it's okay. That's the one with Michael B. Jordan as The Human Torch, Kate Mara as Invisible Woman, Miles Teller as Mr. Fantastic and Jamie Bell as The Thing. The whole thing was pretty good; I guess I was just used to the original classics.
That one's rated PG-13 too.