Easy: England, Australia, New Zealand and India.
Wrong! (At least as far as T20 is concerned.)
Since 2010, these are the 'Win Percentages' for the top teams:
They say in football that the table never lies; and although the West Indies numbers are slightly skewed by having played Sri Lanka 15 times since 2010, winning 11 of those games, with 1 'No Result'; the Windies are also the only team not to have a losing-percentage against England during that period - it is 4-4 there, with one tie.
So I think the conclusion is clear: the T20 'Top 4' are now England, Australia, New Zealand and West Indies.