Really? No Walhart or Gangrel? Or Ashnard? Hell, the Black Knight would have been a perfect character to add even if he ended up as a semi-clone of Ike or even... sword-wielding Ganondorf.
Validar might not have been placed into the game as a playable character since unless you've played Awakening, you're probably not going to know who he is or how relevant he is. Also the fact he's a walking spoiler doesn't help.
The issue with Fire Emblem's antagonists is that most of them don't really do much besides act as a chapter boss. Some do drive the plot, but it's extremely spoiler-y compared to Ganondorf who you knew is evil by looking at him and it's not going to be a huge deal since he's the main villain in over half the games - it's common knowledge compared to revealing who's the big bad of Fire Emblem: Shadow Dragon or Sacred Stones.
Once again, I don't know much about the Japan-only games, but I think one game/series has a regular villain who isn't a "surprise, it was him all along" sort of villain and just wreaks havoc throughout the story like Ganondorf or Bowser. The issue is that it's Japan-only and they're not like Marth who's the first Lord of Fire Emblem or Roy who was promoting Rekka no Ken, his father's, Lyn's, and Hector's game.
Fire Emblem games tend to just have a 1-Villain-Per-Game basis, because basically the cast gets reshuffled each game and very rarely is a boss elaborate in character or repeats appearances. Gharnef in FE 1/3 (11/12) and The Black Knight FE 9/10 are the only moderate examples of it.
Fire Emblem 1&3/11&12:
![Marth :4marth: :4marth:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
's two games as a continued story and its remakes on the DS. The big roots of the series and the one that set up so many standards.
Fire Emblem 2: Used almost an entirely different system that is very rarely cited back. Had the protagonists Alm and Celica.
Fire Emblem 4&5: 5 is... meant to take place between chapters in the latter part of 4 and is a succession story. The first half of 4 is the story of how Sigurd tries to unite the continent, is killed along with some of his men, and then his son Seliph avenges his father. 5 stars Seliph's first cousin Leif in basically more backstory of the Child half of FE4.
Fire Emblem 6&7: The story of Lyndis, Hector, and Eliwood preventing the rebirth of a satanic dragon (7) and then Roy and Hector's daughter Lilina stop the rise of an ancient evil sealed by warriors of old (6)... basically the story of Paper Mario & The Thousand Year Door.
Fire Emblem 8: Erika and Ephiram's game. What's commonly called the weakest of the GBA games and shares many similarities to Fire Emblem 2.
Fire Emblem 9 & 10:
![Ike :4myfriends: :4myfriends:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
's two games in which he goes from the teenager as part of his father's groups of mercenaries to reuniting countries with their true rulers after attempted assasinations (9) to ending up slaying the very Goddess who shaped the world (10).
Fire Emblem 13: The story of the amnesiac
![Robin :4robinm: :4robinm:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
/
![Robin :4robinf: :4robinf:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
who accompanied Chrom as a tactician to end grand wars, fend off against a zombie-like spawn of enemies called The Risen, and ultimately joining forces with
![Lucina :4lucina: :4lucina:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
and other children returned from the future to prevent the revival of Grima. Basically the largest and most popular Fire Emblem game that namely brings together Marth's games and the land of Fire Emblem 2 with about 2,000 years of change after them.
So, when we look at the Fire Emblem reps...
![Marth :4marth: :4marth:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Ike :4myfriends: :4myfriends:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
: The only protagonists grand enough to be the stars of multiple games
![Robin :4robinm: :4robinm:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Robin :4robinf: :4robinf:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
: The far more interesting primary protagonist of the "best" and latest title, which ACTUALLY was an elaboration of a concept from FE12 (which was a duotagonist to Marth, meaning the My Unit also was a protagonist twice)
![RoyPM :roypm: :roypm:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
![Lucina :4lucina: :4lucina:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
: Marth clones added in last minute to promote a game. Roy had the mystery of who he was going to be, Lucina had/has a lot of popularity