I wonder how accurate peoples perceptions are when compared to the facts. Unfortunately we'll never know.
It is possible that they are all equally corrupt (or some other balance), but some are better at hiding it than others.
There is corruption everywhere, it's just the level that differs wildly.
Greece, Spain or Italy are renouned for dodgy shit, Ive heard numerous stories about it and basically their whole society is drenched in the system to a certain extend. While in Scandinavia and north western Europe societies are much more transparent (just look at the top 5 press freedom), corruption is actively rejected and persecuted.
I was aware of the Greek corruption, and not surprised by the Spanish.
I would assume this map generally lines up with reality.
But there could be a few surprises.
In short; will you encounter corruption often?
Does your country have Catholic roots: Yes
Does your country have protestant roots: No