A voice is what makes a Pokemon come to life. Ekans, Arbok and their Japanese counterparts all have very cool voices. In fact, Ekans' cool voice was what made me take an interest in the snakes in the first place. ^_^.
Michael Haigney, the director of Pokemon voice acting, I think, does the voice of Ekans. He also does some other Pokemon like Cubone and Psyduck. Sakaguchi Kouichi is the voice actor of Arbok - Arbok's voice was kept the same as in the Japanese version. You can also occasionally hear Ekans' Japanese voice (such as at Maiden's Peak).
That makes sense, actually. Arbok says its name as "ssshaboku" which fits in with Aabo saying its name as "ssshabo", and the extra syllable on the end of Arbok fits in with Japanese pronounciation.
I don't know who Aabo's voice actor is. It could be Sakaguchi Kouichi too? I really am not sure.
Anyway, here are some clips, sorry they're not very good quality.
Ekans and its partner Koffing dive into attack!
"Ekans! Bind it now!" "Ekansss!"
Jessie orders her Pokemon to attack Sandshrew. (Bad idea. ^_^;;)
"Ekans, Ekans Ekans. Eeekans Ekans."
I think Ekans is saying there's no such thing as a bad Pokemon, only a bad master.
Ekans and Koffing have a conversation with Ash's Pokemon. Bulbasaur causes Ekans and Koffing to worry if their masters have abandoned them.
"Ekans, Ekans Ekans."
Ekans tells Koffing that they'll find their masters.
Aabo again. ^_^.
"SHAAAAAAA!" "I wanted you to cure it, not kill it!"
Arbok doesn't like injections, and Jessie is worried about it. (You can hear Ash saying "woah!" in the background. ^_^.)
Jessie calls her Pokemon out.
"Arbok, poison sting attack!" "Shaaa!"
Jessie gives the order to attack. Woohoo, go Arbok! (It wins this battle, by the way. ^_^.)
Arbok's poison sting attack slashes through the air, hits home and injures the enemy Jolteon.
"Next Pokéball... go!" "Shaaboka!"
Ash finds out he got an Arbok, and tries to remember its attacks.
"Now, squeeze it with your wrap attack!"
Not a good idea, Ash. Arbok wraps it but Jolteon's spikes dig into it and give it an unhappy surprise. :(
Poor Arbok is a bit dazed and confused. Hee, cute.
Useless fact: boku is a form of 'I' (used by guys) in Japan. If Arbok said "boku, Arbok", it would be saying "I'm Arbok", loosely. Cool, huh? ^_^.