It was Ranma's even considering cheating on Akane that ruined the 
story for me completely. He really does come off as a complete bastard.

Remember Ranma trying to convince Shampoo to leave him alone, the first 
time she appeared in Nerima? Rather swayed by her cute face when up 
close. Only momentarily, but then, it's the same in this story. Besides 
Ranma IS a bit of a bastard. He's written as an insensitive, macho, 
chauvinist, not-terrifically-bright young martial artist. Brash and a bit 
of a mouthy show-off to boot. Basically decent, but not exactly a great 
first impression if he existed in real life. He's a bit of a jerk, 
really, but then most 'heroes' are. Either that, or they're noble heroes 
with god(author)-given divine blessing. Ranma 1/2 would be rather boring 
with Dr. Tofu as the hero...