I have only read the op so bear with me.
I think if you do feel that strongly then its not normally a constant - that it ebbs and flows. After all, there are going to be other things on your mind on a day to day basis, whatever those things may be (children, work, parents, friends, etc etc).
There was a male friend who once confided in me that he'd never felt strongly about anyone and had always wanted that rush of love to hit him as he walked through the door to his girlfriend and he was 35 and still looking to experience that emotion.
And as we all know there are folks who experience emotions really strongly and in huge variety from day to day or hour to hour.
I believe it depends on how you're wired.
I know that at times of balance, when I've had plenty of sleep, when I'm feeling healthy and have had a good day, I can EXPRESS more love towards my DP as I'm not tangled up in myself. At other times, when say I've got PMT or something is worrying me I can just find myself being irritable and honestly, he is being the same man in either situation, so it all comes down to me.
Sorry I'm rambling, but those are my thoughts, for what they're worth. I don't think you should beat yourself up if you don't feel a strong emotion that you're perceiving others to be going through. Everyone is different and we can all take our happiness in different shapes and sizes.