Why should Magik be the same character she was in the 80s? Times change,people change, and coming back from the dead and maturing will also cause changes.
I prefered the 80s version of Magik to the 2000s version, with the symbolism and clear arc, but that doesn't take away from the 2000s version. For one, I felt that Simonsen dropped the ball in wrapping up her arc in Inferno. After Claremont left the whole New Mutants team dropped off in maturity and became much more bratty, and her sudden lack of maturity took away from the fact that it was leading up to her big sacrifice. The replacement of Belasco with a completely new demon villain was also a bad move. Being unsatisfied with the New Mutants issues of Inferno I was very happy that they brought her back.
Since returning she went through a full arc (very few characters in comics have arcs at all anymore). She has also been more consistent in her characterization than she was even under Claremont, who for some reason couldn't decide if she was an awkward introvertive outsider or bubly outgoing mall-girl and would vary between them from issue to issue.
For the past 2 years it seems like she has been the only competant adult X-Man in the team books. Like in BOTA, where she was the only one who bothered to investigate the future brotherhood, brought back the future X-Men, and infiltrated the JGS while everyone else was being eaten by Krakoa. Or in Last Will, where when everyone was running around complaining she was the only one to come up with a good plan that could have worked without just killing Malloy. Or Uncanny 33, where when the rest of the team is yelling at Scott she goes and rescues a mutant child.
Another thing that seperates Magik from other comicbook characters is that she actually accomplishes things. She killed Belasco, and he stayed dead. She killed the Elder Gods, and they stayed dead. She ended Limbo, and it stayed destroyed. There's been no annoying 'Magneto/Joker never really died' point.
Legion is the most powerful X-character. He is a fuul-fledged reality warper who can wipe out existence with a thought.
Jean/Phoenix is the next most powerful. She/it is at the weakest a Galactus-level threat.
Magik-sans Darkchilde transformation, can go toe to toe with Thor. With the Darkchild transformation she's Hell Lord level, meaning on par with Mephisto and Dormmamu. And she commands a limitless demon army,some of whom are more powerful than Colossus.
Android Saga is the best. People other than Goku and Vegeta were allowed to be badass and help out. There were multiple interesting villains instead of just one. There were fewer plot holes. And there were actual permanent consequences instead of the Dragon Balls restoring everyone to life at the end.
The Frieza saga abused the Zenkai to the point of stupidity. I was hurt! Now that I'm healed I'm 500 times stronger than I was before! No further training required! That's just unearned. The Kai version has the same problem, but Frieza is a much better villain. And I find that
The Buu Saga began with ruining the idea of Super Saiyan with the kids doing it for no reason an =d Goky just pulling SSJ3 out of his butt. It left no place for non-Sayians. And it has the worst ending of any of the sagas.
The Saiyan Saga is good, but suffers from being short and the fight scenes aren't as good.
Based on performences I've seen I'd have a very different choice for Magik. Maisie Williams, aka Arya Stark. She's actually old enough for the role and has has already shown that she can play damaged/dark teenage girls very well.