lol i like this question and here is my answer to this.
my first pokemon, and i lol when i say this, would be snorlax LOL again.
reason being, he can keep me warm if it's cold, can keep me cool by using his body for shade, and also be my defense against storms. however this could be a downfall if he eats all the damn food!
my 2nd pokemon would be alakazam. and this is due to because of sanity.
I could ask alakazam to put me in a hypnosis sort of state, so i can see things instead of being stranded and could be at a peace of mind, so instead of being in a state of panic or anger, i could be at constant ease.
and my last pokemon but not least, hmmm. would have to be a fire pokemon/flying pokemon as well. probaly would roll with a charizard. i was in a state of curiousity but thinking about it, there is water all around you since your stranded on a island.. and with a fire pokemon, you could boil water so it would take away the salt from the ocean. *smart thinking huh?" and with charizard, i could scout the island to find food and also heat up food if needed.
i'm sold on these three!