I don't see it as "snark". I see it as advice.

Then simply look your friend in the eye and tell him the secret to a happy marriage, bonus points for relating it to how your friend and his woman actually interact.

Example: John, you are strong, masculine, and confident...whatever else....and those are the qualities that attracted [your woman]. Don't lose them. You are the Captain of this ship so it is your job to stay strong, even in the roughest seas, and lead your crew to a safe and happy harbor.

Jill, you are the kindest, sweetest girl we know...whatever is real...and that is why John fell so deeply in love with you. Don't lose those qualities and remember, it takes two experienced hands to manage the ship during the inevitable storms to come....

So work together, love one another, and bring your ship and crew home safely.

You may also check out 1 John 4:7 and The Prophet for further inspiration.