Five reasons why X-Men first class (probably) works so well:
1. No Wolverine. After 4 movies, he has had FAR too much time in the spotlight. With so many mutants, it's about time there was an X-Men movie without him.
[spoiler:269nqejw]He makes a cameo, but it is very brief from what I hear, just one line and it is quite funny. (he says "go fuck yourselves", lolz)[/spoiler:269nqejw]
2. Fresh cast, same mutants. Thanks to being a prequel, we're getting fresh actors without the movie being a goddamn reboot. So we get to see the return of characters from the original 2000 film, without actors returning 11 years after the first film. Don't get me wrong, I loved the first two X-Men movies and the cast (except Halle Berry). But I don't want to see a bunch of 40-70 year old actors running about in costumes. So we get the same Magneto, Xavier, Beast and Mystique but with fresh blood.
3. McAvoy and Fassbender. From what I've read, they nail the roles and have great chemistry. They might not look like Stewart and McKellen, but again, from what I read they have that same rivalry going that we later (chronologically) see in the 2000 X-Men film.
4. Bryan Singer returns, Gavin Hood and Brett "90 minute third X-Men movie, are you kidding me?!" Ratner get the boot. The guy who made the movies work returns, the guys who broke the series are gone. Bonus points for having Matthew Vaughn direct.
5. No 7-11 promotion, no video game adaptation, no Happy Meal, no BK Kid's Club meal.