1. Milotic
2. Salamence
3. Flygon
You can only get the Johto starters by trading from Emerald or XD.
Kanto/Hoenn-migration. Also for Johto but you must migrate from Emerald, after beating the league in Emerald, you go to the Safari Zone and there'll be a new area. In the new area you can find Johto Pokemon including the starters (the starters are EXTREMELY rare to find though.)
cheats
Trading.
Sorry, but the only way to get all the starters from Pokemon Crystal to Fire Red or to Pokemon Emerald is to get a gameshark and do it from there.
You need a game sharkYou need a game shark you can also get them from emerald but you have to complete the pokedex in emerald to get oe of the three starters from pro. berch
catch....... BUT ONLY on emerald
You can never find the starters in the wild you can though find johto pokemon.
You can get it by transferring the Johoto starters via your Game Boy Advance to Pokemon Emerald
T-R-A-D-E that spells trade (with someone) You need emerald , ruby/sapphire and a link cable. pick one of the three starters in emerald. then pick a starter that you didn't pick in emerald. then trade the starter over to emerald. then pick the starter that you didn't pick at all and trade it over to emerald. now you have all three starters in emerald! hope i helped!
You don't not unless you trade or cheat
Only emerald can get a johto starter however you can trade the johto shadow Pokemon from Pokemon colosseum then breed them in sapphire to get the johto starters you can also trade the johto starters directly from Pokemon xd gale of darkness.