It is very difficult to compare different (complex) projects (independently from whether they are public or private) because - Captain Obvious speaking now - they are different (not only the actual thing that is built, also the quality of the project and its engineering, the chosen contractor and a lot of other factors come into play, your new examples add two completely different countries and two completely different periods of construction).
Construction times are even trickier, as they may also be influenced by other factors (authorizations/approvals or changing norms as an example).
A (typical) appropriate construction time for a (large/complex) project is around 4-5-6 years, 3 years means they were fast (in Chicago , in the '70's) 10 years means they were slow (in Slovenia, in more recent years), but otherwise there is no way to make senceful comparisons.
Construction times are even trickier, as they may also be influenced by other factors (authorizations/approvals or changing norms as an example).
A (typical) appropriate construction time for a (large/complex) project is around 4-5-6 years, 3 years means they were fast (in Chicago , in the '70's) 10 years means they were slow (in Slovenia, in more recent years), but otherwise there is no way to make senceful comparisons.