^ ^ yep, apologies for not replying sooner - am on holiday.
Bit gives some pretty good reasons above why not to compare the two. Might add that football at the club level is a lot more "efficient" for want of a better word. What I mean by that is a lot of appointments and selections at the national level are political to an extent. So, for example, Argentina at the last World Cup had Maradona as the manager - and frankly, though one of the greatest players of all time he is not a good manager - his appointment was definitely a political one. Argentina had some awesome players in that squad - they also had some incredible players left out of the squad who probably should have been in there. Messi played in that team and he didn't score a goal in 6 or so games at the Cup - but he scored 56 goals or so in all competitions for Barcelona this season.
Anyway - I just don't compare the two - to my mind two of the best national XI's ever assembled never even won a World Cup - Brazil in 1982 (to my mind the best national XI ever assembled) and France in 1986 (though the latter won the Euro in 84 - in 86 Argentina had a fairly bad side but they ended up winning the Cup because of one absolutely freakish player). I would never pick a club side as one of the best ever if it hadn't of won at least several trophies across a number of competitions - but that criteria doesn't hold for national teams.