1. April 28th, 1980 - Game & Watch
2. May 22nd, 1980 - Pac-man
3. July 9th, 1981 - Mario
4. July 9th, 1981 - Donkey Kong
5. July 14th, 1983 - Luigi
6. February 1984 - Little Mac
7. April 21st, 1984 - Duck Hunt Dog
8. July 26th, 1985 - R.O.B.
9. September 13th, 1985 - Peach
10. September 13th, 1985 - Bowser
11. February 21st, 1986 - Link
12. February 21st, 1986 - Zelda
13. August 6th, 1986 - Samus
14. December 19th, 1986 - Pit
15. December 19th, 1986 - Palutena
16. December 17th, 1987 - Mega Man
17. April 20th, 1990 - Marth
18. July 27th, 1990 - Dr. Mario
19. November 21st, 1990 - Yoshi
20. November 21st, 1990 - Captain Falcon
21. June 23rd, 1991 - Sonic
22. April 27th, 1992 - Kirby
23. April 27th, 1992 - King Dedede
24. October 21st, 1992 - Wario
25. February 21st, 1993 - Fox
26. February 21st, 1993 - Falco
27. March 23rd, 1993 - Metaknight
28. August 27th, 1994 - Ness
29. November 21st, 1994 - Diddy Kong
30. February 27th, 1996 - Pikachu
31. February 27th, 1996 - Charizard
32. February 27th, 1996 - Jigglypuff
33. November 21st, 1998 - Ganondorf
34. November 21st, 1998 - Sheik
35. April 14th, 2001 - Villager
36. October 26th, 2001 - Pikmin & Olimar
37. July 19th, 2002 - Bowser Jr.
38. December 13th, 2002 - Toon Link
39. February 9th, 2004 - Zero Suit Samus
40. April 20th, 2005 - Ike
41. July 17th, 2005/September 28th, 2006 – Lucario (There’s no specification as to whether the movie appearance counts or not)
42. November 1st, 2007 - Rosalina
43. December 1st, 2007 - Wii Fit Trainer
44. June 10th, 2010 - Shulk
45. March 22nd, 2012 - Dark Pit
46. April 19th, 2012 - Robin
47. April 19th, 2012 - Lucina
48. October 12th, 2013 - Greninja
Obviously, this assumes the ESRB leak is 100% accurate aside from the cipher, because I just can't take those last five seriously. Just can't.
Other characters and where they would be, if they're in:
Ice Climbers - January 30th, 1985 (Right after Duck Hunt Dog)
Mach Rider - November 21st, 1985 (Right after Bowser)
Ridley - August 6th, 1986 (Right after Samus)
Snake - July 7th, 1987 (Right after Palutena)
Wolf - February 21st, 1993 (Right after Falco)
King K. Rool - November 21st, 1994 (Right after Diddy)
Dixie Kong - November 20th, 1995 (Right after Diddy)
Ivysaur - February 27th, 1996 (Right after Jiggs)
Squirtle - February 27th, 1996 (Right after Jiggs)
Mewtwo - February 27th, 1996 (Right after Jiggs)
Impa - November 21st, 1998 (Right after Sheik) | Alternatively February 21st, 1886 (Right after Zelda) as she appears in the instruction manuals, but not the game, itself.
Isaac - August 1st, 2001 (Right after Villager)
Krystal - September 23rd, 2002 (Right after Bowser Jr.)
Lucas - April 20th, 2006 (Right after/before Lucario, depending)
Chorus Men - July 31st, 2008 (Right after Wii Fit Trainer)
At this point, I'm not even trying to be realistic, anymore, so I'm just gonna stop before I start going on confirmed assist trophies.