You live in a small town outside of Petalburg (or Oldale) in the Region of Hoenn. A few years ago, you became part of a penpal program and received a penpal in a faraway region [not sure if it should be Kanto or Sinnoh]. Your Penpal's name is <#######>.
You have always talked about going on a journey to visit your PenPal, but you have always been too young, and had never had a pokemon of your own. Today all that has changed. You are finally old enough and you are ready to receive your first pokemon.
After you receive your pokemon, you set out upon your journey. Your first stop is Rustboro City. Roxanne (or other name), the gym leader is outside training, blocking the way out of town. After defeating her you are able to move eastward to the ferry in Fallarbor Town.
You take the ferry from Fallarbor Town to Olivine City in Johto. Outside of town, Jasmine (or other name) the Olivine Gym Leader is knelt beside her Steelix, blocking the way out of town. She doesn't want to leave its side, and asks you to get some medicine from her grandmother in Cianwood.
Surfing South to Cianwood you meet up with (Jasmine)'s grandmother. She isn't sure that Jasmine actually sent you and so makes you battle her in a pokemon battle. After winning, she gives you the medicine, and you take it back to Jasmine. Jasmine then asks you for a battle to make sure Steelix is all better. After winning she goes back to the gym and the way out of town is open.
In Ecruteak they are holding a festival. So instead you go to the Brass Tower. A fire breaks out and you get out of the building. The gym leader sees you as a suspect and battles you. After winning, he realizes that the fire was accidentally caused by Ho-oh, and apologizes.
The next town is Goldenrod city. The forest is off limits to the south and the path to violet city is blocked. so the only path is a detour to the Orange Islands. Your first stop is Alto Mare Island.
In Alto Mare Island, you first meet Team Rocket. At this early point, they have no idea legendary pokemon actually exist and only want to steal the Soul Dew, selling it on the black market for $$$. You meet up with Latios and Latias, and stop Team Rocket. (one of latios/latias then decide to go with you) You are sworn to secrecy about the general existence of legendary pokemon.
Now... off to the orange Islands. Passing a healing spot on T. Island where cataching pokemon is off limits, you head to Kumquat Island. The gym leader is not in right now, so you decide to go off and sight see.
to the south is shamouti island, where you take part in the yearly Legend Festival. At the islands you meet up with the legendary birds. And once all three spheres are collected you meet up with Lugia.
The gym leader of Kumquat Island is in, and you fight her. You're next stop is New Island for a quick rest and then off to Cinnabar. On New Island you once again encounter Team Rocket. On New Island they have a warehouse and have captured Mew and Mewtwo. You defeat team rocket and aide in Mew's and Mewtwo's escape.
Mewtwo thanks you for your help and tells you to meet him at the Cerulean Cave. ...
you make it to the Pokemon League etc. and then start towards Cerulean. However the road is blocked. Team Rocket is trying to capture Mewtwo in the Ceruelan Cave, as well as digging a tunnel to Sinnoh to get at the rare pokemon there. You finish them off and discover that the tunnel was nearly completed. you rock smash the last bit and emerge at Lake Verity, in Sinnoh.
finding yourself finally in Sinnoh, you prepare to meet your penpal. If you play as a boy, this penpal is Delia Ketchum.
congratulations!!! Ash's family story of how they met is complete!
Not sure what happens if you play as a girl. What do you guys think of having the penpals be Gary's parents?