^ Trent is right. Don't forget, X-Men predated LOTR's release and Stewart was really only well-known for Trek. Berry was a long way away from her Oscar and leading lady status. I remember a few previews-of-the-year type articles in the like of Empire and Total Film. They all voiced some concerns that the unstarry cast and fact that the X-Men weren't as well known as Batman might result in a flop. The low-ish budget afforded by Fox also reflected this.
Not sure if it's already been referred to, but Singer has given a little more info about this project and seems to confirm that the Magneto movie is dead:
http://www.darkhorizons.com/news/15967/bryan-singer-on-x-men-other-projects
Allow me to correct this by saying, Halle Berry was already well know and established within the African-American community due to her work as Dorothy Danderage that was widely broadcast on HBO & in Alex Halle's: Queen well before any Oscar win. Both roles won her critical acclaim from both Black & White audiences. From my understanding was that she took the role of Storm because she admired what the character stood for. Let's not forget, Whoopi Goldberg was an Academy award winning actress and still took the role of Guinan and was willing to work for free and uncredited due to the inspiration of Trek on her. So for a large unrepresented audience on this board, Halle Berry's name had well known pull.
TNG was a huge success that reached normally non-Trek watching audiences causing Capt. Picard to be a much referance pop icon, so Stewart was very well known accross the globe due to it.
exodus, I don't doubt either Halle's talent or the respect she was held in. But a box-office draw she was not, prior to X-Men. She was certainly not anywhere near as well known to general audiences as she is now, nor was her situation in any way comparable to that of Whoopi when she took on the role of Guinan. If you look at her appearances immediately before X-Men (
http://www.imdb.com/name/nm0000932/ ), she was in the Dandridge movie, something called Why Do Fools Fall In Love, Warren Beatty's acclaimed but financially unsuccessful Bulworth. Before that, she'd done an episode of Frasier and a tv movie called The Wedding.Prior to that, she was in a critically reviled and unsuccessful movie called B.A.P.S. (Black American Princesses).
Halle now may be one of the most famous actresses in the world but back then, she needed X-Men more than it needed her. Whoopi Goldberg was a big box office draw when she took on a small recurring role in a tv series; Halle was a little-known jobbing actress when she took on a role in an ensemble movie with a bigger budget than anything she'd appeared in since her debut in The Flinstones. At the time of casting, she was much less famous than Angela Basset, who generally topped fanboy wish-lists to play Storm.
Stewart may also have been an icon because of Trek but again, if you look at his non-Trek roles immediately before X-Men, I doubt if you've seen any of them, with the possible exception of his Christmas Carol tv movie. People like him, William Shatner or Mark Hamill may be iconic to we sc-fi fans, but the reality is that outside of their iconic roles, they generally don't put bums on seats in cinemas.