Somewhat similar thread is already here
Anyway, I don't want to dismiss doubles, but I have a feeling that any player would like to have a successful singles career, doubles slams only allow worse singles players to have glory at slams. But as you don't have too many Olympic Gold chances, top players also play OG doubles to get a better chance to win gold.
So, I'd say OG doubles has better quality than Slam doubles, but Slam doubles are more prestigious than OG doubles. So, I'd say they're on the same level, for different reasons. For a doubles specialist, I'd say Slam doubles matter more, for singles' slam winner without an OG singles gold, OG doubles gold matter more.