Belgium was classed first mainly because of the players they had but they weren't so impressive in picking a World Cup for example. For Greece, like any other country, they got a shot and were successful but it was just a shot. It is like Porto winning Champions League with Mourinho long time ago.
Players come and go all the time. France recovered pretty well from the retirement of Thierry Henry, Nicolas Anelka and Franck Ribéry. The same can be said about England after the departure of Steven Gerrard, Frank Lampard and Wayne Rooney. The problem with Germany is that they don't have younger players coming through the ranks. The quality of the national league (Bundesliga) is declining and that maybe one of the reasons. We can't also ignore the demographics. Germany is a rapidly ageing country.
@Sithara007 France was blessed with many talented player’s and they had enough luck to help them achieve their goals but Italy surprisingly lost the plot. Lastly England was always favoured to do well because of premier league rules to keep local player’s in the squad and many even attracted outside leagues attention and further grew themselves which is helping England now e.g. Jude.