>Do you think there’s any legitimacy in my annoyance at the small number of lasting relationships in the MU? Or is Romance a casualty of the long-term medium?>

I think lasting relationships are an inevitable casualty of long-term serial storytelling. Just look at any soap opera—how many times are...

I'm inclined to agree, but the problem is that because they've already had their big, iconic relationship, there's always going to be people standing there saying "Scrap the relationship, and let <character> get back together with (Gambit/Mary Jane/Jean Grey/Piotr/Lois Lane/Iris West etc)", which does kind of detract from it for anyone who talks comics with one of those people.

And it's always been a problem, I know I've read about people who hated Mary Jane because Gwen Stacy was Peter's soulmate.

Even those of us with more open minds will probably compare a new romantic interest with the classic. The iconic relationships are iconic for a reason, and most others are going to pale in comparison.