Deathla, Gryphon, or Bagan?

i would leave Bagan for the last movie

Probably Gryphon. Even though his origins were more or less used for Gyaos in Gamera: Guardian of the Universe.

Definetly Bagan

Bagan, definitely. He deserves a movie, because he was turned down so many times (even though he appeared in Super Godzilla). :(

I don't know much about these monsters, except for what I've read about them online. I'd have to go with Bagan since he seems to be the most powerful of the three and the most awesome.

I'm not a huge fan of any these monsters tbh. I mean I wouldn't be upset if I saw them in a Godzilla movie, but 9 times out of 10 I would prefer one of the already established TOHO monsters or a cool original design. 

After those had been fairly exhausted, and there wasn't much left to pick up, and these were our options....well....

Probably Bagan. Just because he LOOKS the coolest to me, entirely from an appearance standpoint. It wouldn't matter too much if they changed his overall strength or powers so long as it fit what they were trying to do with the film.