I would say Wolverine but they kept going back and trying to explain stuff then retcon stuff and then Romulus existed and now it is even more confusing and straight trash.
Genesis's is cool.
I quite like Chamber's, although given that i spent a lot of my teenage years wearing black leather and sulking, I cannot imagine why
"Generation X was the one, pristine, x-team..."- darknessatnoon
My X-Men Sketch Book
I love Magik's origin. It's too bad that writers since then haven't taken advantage of it fully:
1) The story goes that one set of X-Men were stuck in Limbo, while their Illyana escaped, while Magik is from the (main) timeline where the X-Men escaped and she was stuck in Limbo. Unless I'm not remembering it correctly, the Illyana that escaped Limbo should have been the one found in Magik's armor at the end of Inferno, who died of the Legacy virus, not a "de-aged" Illyana. That would mean that the "real" Illyana is still out there in Limbo. There was no need to introduce an Illyana from the House of M storyline who escaped the reality change back to "normal" (who is "out there in space and time") nor a Belasco-revived version that is around now.
2) The Soul-Sword was created from Illyana's own soul. It wasn't something that give the user control of Limbo and could only be used by Illyana, and Kitty (because of their psychic link) when Illyana wasn't around. The Amanda Sefton stories don't fit, although I did like reading them.
3) Time is out of whack in Limbo. There should be Illyanas, New Mutants, X-Men, and anyone else whose spent time in Limbo showing up out of chronological order. It would be interesting to see present-day Illyana talking to Old Witch Storm who trained her. Or alternate versions of characters traveling with their Illyana. This goes with the fact that present day Illyana doesn't use her time-traveling powers that I've mentioned in an Avx thread.
I like Karma's origin. Very tragic. She hasn't been used as effectively as she was in her first appearance when she was able to control the entire Fantastic Four and used them to fight Spiderman. She was weak from malnutrition at the time, which made that feat more impressive.
Magma has a good one, if you ignore the Allison Crestmore stuff. I love that Selene is her great-plus-grandmother.