Calvin's parents from Calvin and Hobbes are quite loving, despite the stress of having a kid like Calvin. Or possibly because they have a kid like Calvin, moments of peace and restaurant dates are so much more enjoyable (even if Calvin's dad keeps turning his head because he thought he heard sirens).
In Zits the loving, stable marriage between Connie and Walt Duncan infuriates their son, Jeremy, by adding to their general dorkiness: their happy stability makes him too well-adjusted to have a tragic backstory. One strip shows the parents talking and laughing over doing the dishes, prompting Jeremy to sigh, "The award for 'person whose life least resembles MTV' goes to..." (or something like that.)
Roger and Andrea from FoxTrot (much to Jason's disgust when he sees them kissing). Despite every crisis they've been through (Roger quitting his job, Andy desperately acting young again, the many horrible, Horrible Camping Trips), their love shows no signs of faltering.
Bob Weber's Moose and Molly are heavy-set, low-rung blue-collar types, totally blissed out on each other.
One Big Happy has two generations of married couples and a couple of children living in the same house.