As other reviewers have pointed out, X-men First Class and Wolverine are not region free, they are region B (however they still play perfectly well on something like a PS3 for example but may not work on specific blu-ray players so keep this in mind). However, luckily because I had the PS3 I had no trouble watching all of the movies and I can say without question that I am so glad I decided to invest in the blu-ray copies.
I'd previously seen all of the movies before in standard format, and they're brilliant, but with the addition of this high image and sound quality they just look fantastic. Things like people's skin, their teeth, the landscape (for instance one particular scene focuses on a water droplet on a leaf which looks so clear and detailed that you can see as much as the wax of the leaf). I expected that the movies would look great but it seems that the sound has been enhanced as well. I noticed this the most with Wolverine (the character, not the movie). When someone comes into contact with him we hear this really clear metallic noise which was barely audible in the standard versions. But also things like footsteps are enhanced - I definitely recommend listening out for all of the new things which before we couldn't appreciate as much.
As for the movies themselves - who doesn't love shape-shifting, weather weilding, metal-filled, life-sucking mutants? Well the humans in this case. I love getting to see all of the characters and what their different mutations are, the introduction of new characters as the films progressed is nice too. The best film by far has to be X-Men: First Class which is essentially a prequel to the whole series and we get to see the young version of our favourite characters (and we get to learn things about the characters which we may have had questions about for two or three movies, like how Xavier was paralysed for instance).
Well worth the money. Hope this helps.