What country are you looking at?

Using the UK National archives http://webarchive.nationalarchives.gov.uk/20160105160709/http://www.ons.gov.uk/ons/search/index.html?newquery=baby+names&newoffset=50&pageSize=50&sortBy=&sortDirection=DESCENDING&applyFilters=true

The file 2004 Baby Names Statistics Boys (Excel sheet 1258Kb) had the top 100 names for every decade since 1904

In 1904 and 2015 there were three names which were in the top 10 for both lists; William, George, and Thomas. Plus I would say Charles / Charlie are very closely related and just a slightly modern take on the same name.

So there is definitely some continuation of names across decades, with the notable point being though that three of these names are all traditional royal family names which have been common for hundreds of years, with William and George having been given a boost in popularity by the new Royal births in the last few years.

On the flip side, David, which was top in the 50s and 60s had fallen to 43 in 2015, and none of the top 10 in the 50s was still there by 2015 even though there was 5 still around in 84.

For the UK, in the last 120 years, it seems very common for popular names to have a large turnover roughly every 30/40 years. But, there are also a core group of names that no matter what the current trends, seem to stick around the top 30. This also seems to be far more the case for boys than girls, where there is less consistency over longer periods.

I have no proof, but I think a certain amount of this is going to be people copying the names of the Royal family, of which we have had far more kings than Queens. As the Royals continually recycle the same names for the heirs to the throne you see certain names constantly reappearing within the celebrity influence. This has an impact for baby girls, see Charlotte in the recent top 10 list, but even the Royal Family seem to use a larger variety for the female non heirs (Zara, Beatrice, Eugenie for example in the latest round)