There are many methods. You could trade from the GTS in Goldenrod city. Or you could catch a Ditto and borrow a starter from your friend, breed them together and then return the ditto.
i am sure you can see them but not catch them
with an AR
You can not the get all starters in any game.The closest one is HeartGold and Soulsilver
Totodile, Chikorita, and Cyndaquil.
Trade with other people who have heart gold or soul silver.
After you defeat red, Prof. Oak gives you ONE of the starters, but you cant catch the starters nor get all of them at once
all the previous starters, you get to pick one from each new edition... or at least that's what I've heard. sorry if I'm wrong X(
There joto staters
All Kanto/ Johto PKMN excluding starters (although you can get two from each reason
no but you can get the kanto starters (bulbasaur charmander squirtle) and the hoenn starters (treecko torchic mudkip) but you need to get all 16 badges
For the Johto starters, you get them at the very beginning of the game. As for the Kanto starters, one of the three (your choice) can be obtained from Professor Oak after obtaining all 16 badges.
chikorita,cyndaquil, totodile