The key is to avoid humblebragging, but also diminishing accomplishments and fake modesty.
Non-runners tend to know a marathon takes about 4 hours to complete, that would be the "norm". Anything in the 5-6 hours range is clearly slow to them, anything in the 3 range sounds pretty good, and anything that starts with a 2 puzzles them.
So as the previous poster said, give context.
If you ran 3:02, tell them you were working towards a BQ and that your next goal is sub 3 which is 6:52 pace per mile.
But if you ran 2:30, you can't fake modesty and be like "it's 5 min something miles". It's clearly fast, even if almost half hour slower than the winner. So I would say that you're pretty happy with your result even if way behind the winners or even OTQ.
I repeat. No fake modesty. You have the right to be happy with your running. Just find the balance between bragging and unnecessary modesty. Know your audience, and adapt accordingly.
The best quote is definitely the people asking how far was this marathon? As if there were different marathon lengths.