"Without Vishnu, life has no meaning."
Same statement, same problem: it's a non-sequitur.
Why is life meaningless without a higher being to give it meaning? Why is the higher being the only one that can give life meaning? Why can't lower beings give their own lives meaning?
On another note, does the higher being's life have a meaning? If there's not an even higher being to give that lower higher being's life meaning, then, by the theist's own logic, the lower higher being's life has no meaning. And, on that note, why should I trust someone whose life has no meaning to give my life meaning?