Wow... Long debate XD
(not intending to join in though...)
I think I agree with the part where their marriage might not turn out well and that it wouldn't be very healthy D: (even though I don't wish for it to be that way D:)
But I still think that Shinichi does love Ran despite being overly enthusiastic over his cases. I actually see 'running off for a case when he's with Ran' something like a child running off to a candy store when he is with his mom. A childlike behavior, but I don't think it is because he doesn't love her enough. I think it's more like a habit or that Shinichi takes Ran a little too for granted. Maybe when he loses her, he'll know how much he loved her then.
Anyways, I support shinran!!!! <333