Neither and both.
Buffy had a very important job to do, something that Riley never did seem to grasp. As Buffy said, demon fighting was an adventure to him, something that he could walk away from at any time. To Buffy, it wasn't just a way of life, it was the way that she was going to die, an inescapable fact, and she was reminded of that fact every day. What little time that she had away from Slaying was very precious to her, as well as very limited. Riley never really realized that the quiet times that she chose to spend with him were all that she had to give.
On the other hand, Riley had what I call a Sir Galahad complex. He wanted to be the hero, the protector, the defender, and the savior. That was undoubtedly why he went into military service and almost certainly why he was part of the Initiative and later why he left Sunnydale to go back into the Army. It was the only way that he could once more be the one thing that he had always wanted to be, and the one thing that he had no hope whatsoever of ever being on the hellmouth. The best. As long as Buffy was there, he was never more than second best, and once Spike began seriously fighting demons, he slipped back even from his Number 2 position.
Buffy, I think, genuinely wanted to love Riley. She even went so far as to tell Angel that she did love him. And Riley most definitely wanted to love Buffy, but he wanted her to need and depend on him to a degree that she simply couldn't manage. As she would say several years later, it was the mission that counted, and Riley was never really a part of that mission.
Each wanted something that the other couldn't give, and neither could really completely understand why the other couldn't be exactly what they wanted and needed them to be.