Surely Blastoise was a superb Pokemon.
Strong, reliable, didn't die easily, very good powers, and a water pokemon as well.
Hydro Pump was superb.
EDIT: But that was the normal pokemon, the best Pokemon was Mewtwo!!!
Mewtwo on Gameboy rocked.
I also had a friend who's dad owned a gameshop, and in the japanese gameboy version they had mew - but he was really rare.
Luckily, there was a method to transfer Mew onto the normal gameboy me and my friend had (UK Version) and my pokemon battle time was as follows:
Blastoise - Everything to max.
Charizard - Everything to max.
Zapdos - Everything to max.
Mewtwo - Everything to max.
Mew - Everything to max.
I never lost a game, ever.
I forgot to mention Exeggutor, he's also seriously good with the right moveset.
Most common moveset is probably leech seed/double edge/solar beam and then either stun spore or sleep powder.
leaf green and fire red will be cool, going through kanto again, in full colour! Oh yeah, in blue i had 2 Mewtwo, the three legendary birds and i forget the last one i had (spot the mewtwo fan).
In silver i had more common pokemon, but i've forgotten which.
In Ruby i have Flygon, Salamance,Absol, Mightyena,Metacross and my Blaziken, but she's just untill i find a way to get a mewtwo on the game!