Dear Keeping Up,
Good for you for wanting to rise above the "who signed the mortgage papers first" competition. It's not fun, it doesn't help you celebrate each other's successes and it can go on forever if you let it. Still, you're right that comparisons are inevitable, and you'll benefit from having a few simple ways of dealing with these friends. You'll also benefit from being secure in your life choices and not feeling the need to justify, defend or champion what you're doing.
When it comes to weddings in particular, people often take on an alter-ego (no pun intended) during the course of the planning. You might have to limit your exposure to certain friends in between the proposal and the chuppah. If friends ask you about timing, encourage them to make the engagement long enough to plan a party and short enough not to take over their lives. Lend an ear, but don't stand for any bridezilla nonsense. If the sheer fact that couples are getting married is making single friends jealous, well, that's an unfortunate part of being an adult. Of course, the engaged folks can minimize the damage by finding other things to talk about, at least some of the time.
I happen to think that the home-buying process can be a great bonding opportunity for friends. My husband and I enjoy comparing notes with friends who are buying or thinking of buying. Again, if it becomes a competition for the most square feet, the newest granite, the shiniest stainless, etc., then it's no fun. But if that's really the MO of these friends, I'm not sure what part of the friendship you're trying to salvage in the first place.
Finally, when it comes to babies, this one, more than any other, is a game changer. As much as I resisted the idea that kids would irrevocably change my social life (along with everything else), becoming a parent, more than any other life stage I've experienced, really does change everything. Suddenly, the parent's life operates on a completely different timetable than the non-parent's life, poop becomes an unavoidable focus of conversation, and a pen cap on the floor becomes not just a nuisance but an immediate sign of danger. If some friends are having babies and others aren't, a natural divide often occurs that can strain friendships. But that divide also resolves if and when the rest of the friends enter that stage themselves.
My husband and I have been very lucky that our non-parent friends love our daughter and want to hang out with her (and us). At the same time, there's a sense of relief when another couple close to us has a baby. It means someone else gets it, someone else is willing (eager, even!) to talk about poop, someone else will have a baby-proofed home where we can spend an afternoon. I don't feel that way when my friends get married or buy a house, but a baby means we speak the same language again.
As for those simple ways of dealing with competition, when your friends start in on the next big thing in their lives, listen in a supportive way. When you've heard enough, find a way to change the subject. If they're telling you for the millionth time about the paint chips for the new bedroom, change the subject sooner. If they make comments that you find hurtful or objectionable, whether it's about your life choices, theirs or anyone else's, or, really, just in general, let them know that it bothers you. Finally, as difficult as it may be, there are certain times in your life when certain friends will be a better fit for you than others. If you need to take a break from this crowd until the competition dies down or until you're all back in the same phase, don't feel bad. Embrace it as a time to make new friends but keep the old. And, if you don't keep the old forever, that's O.K., too.