Mew
Me - oo
Put emphasis on the double o
Mewtwo
Me-oo-two
Same as mew but with a two on the end
Articuno
Ar-ti-coo-no
Arr, as in like a pirate, ti as in like tea, coo as in coolio, and no as in no way!
Zapdos
Za-pdo-s
Za as you say normally and like the name 'Zak'
pdo as you say normaly a P then you short it to a lower cade d so a 'du' sound. And then sliding into an o. And then an S at the end. Za-pdo-s, Zap-dos, Zapdos
Moltres
Mol-tre-s
Mol as you say 'Molten rock'/'lava' and then 'tres', spanish for three
Dragonite
Dragon-ite
A normal Dragon saying, and then the end of the rod, kite - ite.
Dra-gon-ite
Look at the end of the three birds, they all have a spanish number on the end.
Moltres - 3 - Tres
Zapdos - 2 - Dos
Articuno - 1 - Uno
There isn't a right or wrong in pronouncing there names, just the way you want to say it.