"God bless you" is the normal expression to use. Actually, it is part of the expression:
May God bless you.
This type of sentence — with "may" acting as a kind of imperative
verb,but often understood and unstated — occurs sometimes in
sentences that ask God for help. "God bless you" and "may God bless
Perhaps in recent times you've heard the song "God Bless America." In
that song, people are really saying "May 'God Bless America.' We are
hoping for that." When you say "God bless you," you saying that you
hope God blesses the other person.
"God blesses you" is not a set expression. It might, however, be used
in a sentence like this: "God blesses you every time that you see a
baby smile, that you smell the flowers in your garden, that you recover
from an illness." Of course, this kind of sentence occurs much less
frequently, only when you are describing — not asking for — blessings
I would imagine that in today's world, people are using the first
construction even more than usual.
Sentence like these are heard, particularly in religious or perhaps
(May) God save us!
(May) God grant us strength.
(May) peace be with you.