mmm, well, how to tell you this better? I'll just show this to you in numbers:
Kyogre: Max Speed: 279
Max SAtk : 399
Pikachu:Max Speed: 279
Max SAtk : 398
Pika with Light Ball of course. Nice, eh? Now, to answer your question.
Yes, a Volt Tackle Pikachu holdin a Light Ball is GOOD!! But remember that Volt Tackle is the electric version of Double Edge. And although Volt Tackle WILL do a LOT of damage, the damage you will receive back is also great. And Pika being as frail as he is, he won't survive much anyway, getting damage from his moves back doesn't help one bit. It's kind of a suicide set. But if you want to give it a try, be my guest. If you don't like what he's doing, just put thunderbolt back on. And it works much better on Pikachu's greater spatk than on Raichu. Raichu will survive a little more, but won't do the same damage to save his life.