1. Mila
2. Cyber Raidou (if he actually counts)
3. Rig
4. Nyotengu (again, if she counts)
Picked up Mila in vanilla because no Leon OR Ein (and I wasn't good with anyone else at the time) and for the most part she has been the only female DOA character whose design and fighting style I actually like. Haven't touched her much in Ultimate but I can still pull my weight with her when I need to. One of my friend's reactions to when he found out I played Mila was "You play female characters now?"
Cyber Raidou because I briefly touched him in Dimensions and had a blast with him (never played him in 1) and he has Offensive Holds (given my character preferences...).
Rig is that cool guy that hangs out with Ein on the street corner, sure his wardrobe is lackluster but he has that "cool guy" vibe that Ein's got (but will never surpass). I'll continue putting off learning him but he's right there with a design and style I've grown to like (watching Jaegar play him also is extremely entertaining).
Nyotengu because Bankotsubo spiritually lives on (if having her as a "newbie" really counts along with Raidou).
Don't really care too much about the others.
Momiji and Rachel were just other characters to play as in NG when I would have preferred to stick with Hayabusa, if they hadn't made it into DOA I wouldn't have cared much.
Phase 4 was fun to play in the first couple weeks and I would probably enjoy playing her again but if she had more of a difference visually between herself and Kasumi I wouldn't be so drawn away from her (Hayate is the only ninja I care to actually play as, Phase is fun offline).
Marie Rose is there with P4 but I really don't care to play as an "18" year old child.
Honoka looks fun to play as but lacks originality in her own right aside from her "Death Stance" If she had more original moves like Raidou I would give her more of a chance than as someone to clear command training and combo challenges.
Pretty much the same for me.
I wasn't gonna even get 5 until I saw Mila, who, in her C2, is the hottest DOA girl I've ever seen, and she inherited Leon's mount tackle to make up for him being absent. Mained her nonstop, never touched anyone else in vanilla. I'm better with Leon since his return, but I've gone back to Mila to get better with her again. I pretty much only play the two of them. Mila was and still is the only time I actually liked one of the DOA girls.
Cyber Raidou just because "power ninja" even though I hate his new look.
Rig, just because he's actually original to DOA, even though he's an exact copy of most western protagonist designs plus Jake Muller from RE6.
Nyo because she made Tengu fit in, when the main complaint was, aesthetically, he was awkward.
I don't like marie rose in any conceptual way, in fact I outright hate her for attracting all the pedos and ruining any image searches for DOA. (if it weren't for that disturbing C2, it probably woulnd't have been that bad)
and Honoka and P4 fall under the "lazy copy paste" category, both with absolutely bland designs and minimal effort put into their designs
And I actually forgot about Momiji and Rachel until I read other posts. Could care less about Momiji, she's just another ninja to me, albeit the most boring to fight outside of a teleport spamming busa.
Rachel on the other hand, I hate for fucking up Nicole's awesome moveset. I've tried over and over to learn Rachel now that Nicole's gone, but they are just NOTHING alike.
so, an official list
1) MIla
2) Raidou
3) Rig
4) Nyo
the rest range from "Couldn't care less" (P4, Salad, Momiji), to outright HATE (Rachel, Marie)