So looking at Atlus's YouTube channel, for some reason I feel like ranking the views on each character's trailer video. There is a large gap in view between pre- and post-delay announcement videos so I'm ranking them separately, lowest to highest.
PRE-DELAY
Maxima - 20,050
Goro - 20,418
Andy - 22,390
Benimaru- 26,396
Ash - 27,458
Joe - 31,625
Yuri- 32,509
Kula - 33,368
Billy Kane - 34,567
King - 36,752
K' - 43,726
Terry - 50,029
Saiki - 56,579
Kyo - 65,735
Mai - 67,863
Flame Iori - 109,812
POST-DELAY
Robert - 4,933
Mature - 5,183
Vice - 5,314
Ryo - 5,495
Takuma - 5,690
Raiden - 7,314
Hwa Jai - 8,060
Chin - 8,064
Duo Lon - 8,128
Shen Woo - 8,132
Ralf - 8,703
Kensou - 8,877
Clark - 9,077
Claw Iori - 9,191
Kim - 10,135
Leona - 10,463
Athena - 11,242
Elisabeth - 13,267
If you wanted to break that down into most popular character per team:
Japan: Kyo
Fatal Fury: Terry
Art of Fighting: Takuma
Kim: Kim
Psycho Soldier: Athena
Elisabeth: Elisabeth
Ikari Warriors: Leona
K': K'
Women Fighters: Mai
Yagami: Iori
So yeah. I don't think there are any real surprises there.