Voldemort could indeed have chosen Neviile, or anyone instead of Harry, but he thought that Harry fit the profecy best. Also, choosing Harry made him his equal, and Voldemort could not turn back after choosing him.
It has been suggested that Voldemort chose Harry to be the boy of the prophesy because Harry, like himself, was a Half-blood. Voldemort feared another half-blood prodigy like himself, and like Dumbledore. Harry's mother, being muggle-born, is not seen as a witch at all, by the thoughts of blood purity, so Harry is considered half-blood. Dumbledore's mother, Kendra, was mentioned (by Aunt Muriel) to be a muggle-born witch as well, and also thought by some to have feigned blood purity.
Yes, and if Voldemort did choose Neville, he would have sucessfully twarted the prophecy (unless Augusta was there) because there was no Death Eater to beg Voldemort to spare Alice. The Dark Lord would have killed both parents, turned the wand on Baby Neville and won.