>>56513746>Why did they screw over Grass starters so much in the beginning?In Gen 1, they all had a BST of 425 but Vensaur was clearly the best option. Stats aren't everything but its best stat was Special, compared to Charizard's Speed and Blastoise's Defense. Since Special functioned as both attack and defense, it had an effective BST of 525, compared to Charizard and Blastoise's 510.
Venusaur is the only one whose stats were effectively unchanged in Gen 2, with its 100 Special becoming 100 SpA and SpD. Charizard and Blastoise only had 85 Special, but they were generously compensated by not only getting 100 in a new Special stat to keep them on par with Venusaur but an additional +9 and +5 on top of that.
>Any why did they favor Fire starters so much?This is just an artifact of Gen 1, 2 and 4's starters all having the same BST. If you standardized them all to 530 the "trend" would mostly disappear. There's still the outliers of Delphox having 534 and Swampert having 535, but those are the only two instances of one starter being arbitrarily granted slightly more stats. It just so happens that a Grass starter never got that slight edge over 530, and since Gen 6 they seem to be consistently standardizing starter stat distributions at 530 BST, so it probably won't happen in the future.
The difference of +/-5 total stat points is extremely marginal and has not influenced the relative viability of any of these Pokémon as much as other factors like the distribution of those stat points, their abilities, secondary typings, movepools, etc.