In Super Smash Bros. 3ds, the unlockables are:
-Ness (Play 10 Vs. Matches)
-Falco (Play 20 Vs. Matches)
-Wario (30 Vs. Matches)
-Lucina (40)
-Dark Pit (50)
-Dr Mario (60)
-ROB (70)
-Ganondorf (80)
-Mr. Game&Watch (90)
-Bowser Jr. (100)
-Duck Hunt (110)
-Jigglypuff (120)
For the Wii U version, they are:
-Falco (10)
-Wario (20)
-Lucina (30)
-Dark Pit (40)
-Dr. Mario (50)
-ROB (60)
-Mr. Game & Watch (80)
-Duck Hunt (100)
The best way to unlock all the characters is really to just set the rules to 1 stock and jump off 120 times. After that, you'll have them all