You are not seriously suggesting that Roger Moore deserves to be in the top 5 because of James Bond

. I cannot even justify that comment with a critical response. Laughable, ha, ha, ha, ha!!!
I think Empire's readership is widely dispersed across the age ranges although you would have to check with the magazine for details. However, I think that most very young readers would probably not be voting for actors over the age of fifty anyway. I don't think you can classify De Niro and Pacino as appealling just to a young audience after all they both began starring in their own films in the late 1960s and reached international fame in the early 1970s. That is only 7/8 years after Clint first came to real international fame in the dollars trilogy - therefore I would say they are in a similar age bracket for appeal.
Without getting into a major debate about te quality of the above mentioned actors output over recent years it's fair to say that with the exception of Mystic River Clint hasn't exactly been on top form recently. For instance Space Cowboys was no Unforgiven or Dirty Harry in the same way that De Niro's The Score was no Goodfellas or Godfather part 2.
I'm not sure that those arguments stand up as reasons for Clint not climbing higher - I think it may be down to differing national tastes in film styles and genres. As I said in a previous post I would have had Clint as the leading 'God Among Us' but am think of reasons why he wasn't rather than saying 'stupid Brits'.