Just a stupid theory of black holes

I was just thinking, do you think it's possible that black holes cause gravity? There is supposed to be one in the center of each galaxy, and maybe their "sucking" power is so tremendous, that black holes is what causes objects to fall. I know it sounds stupid, but hey, I tried!

Every mass has it's own gravity, from an apple to a blackhole. If blackholes were what caused gravity wouldn't we have been sucked off earth ?