I don't even know how to pick a character in the first place. Besides aesthetics at least. Do people have some obvious way they choose a main? I look at SFV and I don't really know who I want to main. I think I liked using Chun Li in SFIV, but that was ages ago. Cammy has always looked fun to me too.
Even if I go and try all of them out, it's not like I use them properly to actually get a good feel. Plus, sometime it dilutes the characters. They all end up seeming the same (apart from obvious differences).
I did thoroughly enjoy using Tina in DOA5 though, so maybe I should first try Rainbow Mika. I never used to like grapplers, but Tina changed me.
It helps trying to distil what core principle you like about the characters you end up maining in various fighting games. Aesthetics can play a part in your choice as well - I for example can't muster up any interest for walking animé clichés like schoolgirls - but that sort of interest is only skin-deep, ultimately. To give you a more concrete example of what to look for, though:
I personally tend to gravitate towards characters that either have deceptive movement in 3D fighters (Yoshimitsu in Tekken, Voldo in Soul CalibEr, Aoi in Virtua Fighter) or are loosely based on counter-gameplay (Goh in VF and Bayman in Dead or Alive), whereas in 2D fighters I have a penchant for characters who either have superior range than most other members in the cast or just end up being fixated on zoning to a certain degree. We're talking about Peacock in Skullgirls, Dhalsim in Street Fighter, Billy Kane + Duo Lon in King of Fighters and so forth. I'll elaborate more on the latter category to paint a clearer picture. Part of the reason for me taking a liking to these is quite frankly me compensating for my lacklustre combo execution - I for the life of me can't play anyone requiring dexterity in order to reach his/her full capacity - but the primary motivator here is that I just like the idea of playing someone who (ideally speaking) is vulnerable up-close, but has the keep-away tools to fend off whatever offensive approach your opponent may be resorting to. It's the dynamic in itself that hooks me: rather than focusing on maximizing your damage at every chance you get up close and personal, I'm moreso inclined to constantly keep an eye out for openings that allow to slip through general strategies, all the while slowly chipping away at the enemy's health pool for carelessly (whether or not unbeknowest) overextending. Maybe even apply a couple of my own set-ups or unexpected aggression when the moment is right depending on the tools at hand, since changing the established pace tends to confuse less experienced players. Anyways though: if I mess up, against good players there's a high chance that the round is a done deal but it's
this exact intensity that compels me... even if it is an exhausting endeavour at times.
In other words: it's the match-up related tactics that the zoning archetype (usually) exemplifies that bring me far more enjoyment than going through standard combo motions, because persistent attempts to push one another outside their comfort zone and forcing one another to adapt to an (almost exclusive) ruleset. It's why Dhalsim vs Zangief (+ other slow grapplers) are my absolute favourite in Street Fighter: on a competent skill level, both of them demand meticulous understanding of their distinct abilities and they're simultaneously stellar opposites with sufficient options available to them to turn the tide in how the match flows. Zangief gets poked all day by Dhalsim and it's a difficult wall to break, but the stress gradually piles up thanks to his high health pool allowing him to push Dhalsim towards the corner just by presence / careful movement alone, or inch just close enough to land a crucial SPD if for example Zangief dances around his anti-air ranges with each jump-in.
tl;dr The above is very much a... highly specific anecdote, but hopefully I got some points across in how to look for what really resonates with you in a character. And for what it's worth, although quite irrelevant: I'm looking to toy around with Birdie and F.A.N.G alongside Dhalsim in Street Fighter V based on these preferences.
