Robert De Niro: Good Genes or Good Docs?

Robert De Niro is the godfather of good looks!

Here’s a 27-year-old version of the young A-list actor at a dinner in New York City (left) and 46 years later ... the Oscar-winning goodfella -- who celebrated his 73rd birthday earlier this week -- at a festival in Bosnia (right).

'Untouchable.'

The question is ...