To the original poster: You appear to be operating under the "hollywood" misconception that a black hole somehow "sucks harder" than the same amount of mass in a non-black-hole form. However, this false "black holes produce an enormous sucking" misconception is one of the many, many concepts of physics that "hollywood" gets totally wrong; a black hole of a given mass produces exactly as strong a gravity field as an object made of "normal matter" having the same mass. If, for example, the Sun were somehow instantaneously replaced with a 1 solar-mass black hole, the orbits of all the planets in the solar system would remain unchanged in the slightest, and the only way anyone would know anything had happened would be that "the Sun suddenly went dark."
Nor despite superficial appearances is the galaxy a "bathtub vortex" draining down the central supermassive black hole; as other posters have noted, the spiral arms are not "streams of matter," but rather concentrations of bright, hot, short-lived stars that form in the wake of "density waves" propagating through the gas and dust of the galactic disk.
Thus, as other posters have noted,stars do not "fall into" the central supermassive BH for the same reason that the the planets do not "fall into" the Sun: They are in stable orbits around the galaxy.
Moreover, please also note that the mass of the central black hole in a spiral galaxy is minuscule compared to the mass of the galaxy itself --- only a small fraction of a percent --- albeit that mass does appear to be correlated with the mass of the host galaxy, see e.g. http://iopscience.iop.org/0004-637X/737/2/50/. (Why the mass of every supermassive BH appears to be about the same small fraction of a percent of the total mass of its host galaxy is still an open question.)