Originally Posted by
Heroine Addict
Jean Grey: Sept., 1963 (The X-Men #1)
Polaris: Oct., 1968 (The X-Men #49)
Storm: May, 1975 (Giant-Size X-Men #1)
Magik: May, 1975 (Giant-Size X-Men #1, as child; Uncanny X-Men #160, Aug. '82, as young adult Mutant)
Psylocke: Dec., 1976 (Captain Britain #8; New Mutants Annual #2, 1986)
Mystique: May, 1978 (Ms. Marvel #16; X-books thereafter)
Aurora: Apr., 1979 (Uncanny X-Men #120)
Kitty Pryde: Jan., 1980 (Uncanny X-Men #129)
Emma Frost: Jan., 1980 (Uncanny X-Men #129)
Dazzler: Feb., 1980 (Uncanny X-Men #130)
Sage: Apr., 1980 (Uncanny X-Men #132)
Karma: Dec., 1980 (Marvel Team-Up #100; Marvel Graphic Novel #4: The New Mutants, 1982)
Rachel Grey-Summers: Jan., 1981 (Uncanny X-Men #141)
Siryn: Apr., 1981 (Spider-Woman #37; X-Force #1, 1991)
Rogue: Nov., 1981 (Avengers Annual #10; Uncanny X-Men #158, 1982)
Dani Moonstar: 1982 (Marvel Graphic Novel #4: The New Mutants)
Wolfsbane: 1982 (Marvel Graphic Novel #4: The New Mutants)
Magma: Oct., 1983 (The New Mutants #8)
Meggan: Dec., 1983 (Marvel UK's Mighty World of Marvel #7; first American appearance is in New Mutants Annual #2, 1986)
Husk: 1984 (Rom Annual #3, and New Mutants #42 in '86, as child; X-Force & then X-Men titles, 1994, as young adult Mutant)
Firestar: May, 1985 (Uncanny X-Men #193; transitioned from original, animated creation, on Spider-Man & His Amazing Friends, in Sept. '81)
Boom-Boom: Nov., 1985 (Secret Wars II #5; X-Factor & then The New Mutants, later 80's)
Frenzy: May, 1986 (X-Factor #4)
Skids: Aug., 1986 (X-Factor #8)
Jubilee: May, 1989 (Uncanny X-Men #244)
Domino: Feb., 1991 (New Mutants #98, impersonated by Copycat; X-Force #8, Mar. '92, for the real Neena)
Monet: Sept., 1994 (Uncanny X-Men #316)
Marrow: Sept., 1994 (Cable #15, as child; X-Men & Generation X, later 90's)
Blink: Oct., 1994 (Uncanny X-Men #317)
Cecilia Reyes: June, 1997 (X-Men vol. 2 #65)
Stepford Cuckoos: Nov., 2001 ( New X-Men #118)
Dust: Dec., 2002 (New X-Men #133)
Surge: Jan., 2004 (New Mutants vol. 2 #8)
Laura Kinney (X-23): Feb., 2004 (NYX #3; transitioned from original, animated creation, on X-Men Evolution S3, prior to)
Armor: Oct., 2004 (Astonishing X-Men #4)
Pixie: Nov., 2004 (New X-Men: Academy X #5)
Oya: Sept., 2010 (Uncanny X-Men #528)
Bold characters = who I feel, have stood out over the years, as the most significant, prominent players of the franchise. I'm trying to determine who the top 20+1 are, and this collected, chonological data was an attempt to help with that, amongst some other things... patterns, I think it shows.