Bruce and Clark are ~45 in my mind. Oliver like 49. I would say Barry is 39 or so. Not sure about the exact ages of Hal or Arthur, but I'd say around that range.
J'onn and Diana age slower so it doesn't really matter.
With the Titans it gets screwy. I would say most of them are probably in their late 20s. Wally and Roy are the oldest, probably in their early 30s already. Beast Boy and Raven are the youngest, around the same age as Jason Todd, who is 24.
Young Justice...let's just say they are all 19/20 or so. Bart ages slower.
Damian is canonically 14. Jon is canonically 16.