>>47060972Fire type is the most likely type to be underserved of the three starter types. Water is one of the single most common types in the game period, and every game except gen 5 has held the promise of grabbing Gyarados, who is usually hand over fist better than the water starter anyways. Grass types are rarer in theory, but tend to be provided in number early on. Additionally, grass types perform disproportionately poorly in most single player playthroughs, as lots of stuff resists Grass, and the Grass type is known for having notoriously shitty movepools, especially in single player where coverage is king.
Even a shitty fire type starter is likely to be handy, as early fire types are nearly unheard of and the few that crop up, like Slugma, tend to be impossibly shit, and they tend to do very well against the early game menagerie of bugs and grass types. The type itself is pretty useful in the TAC environment of single player as well; Fire is actually incredibly underrated as a defensive type.
If you actually know the pokemon distribution of a game, then great, pick the one that best fits the game, but if you're going into a new game or romhack blind, you are almost always best served by grabbing the Fire starter, since the other two can almost always have a proxy caught for them early on.