French revolution laid the foundation of democracy.          
Arguments in favour- 
Greeks especially from Athens are described as the father of democracy, and true indeed they got the ball rolling. 
However the greek form of democracy was nothing COMPARED to what we know as democracy today.
 It wasn't representative and it only was for a chosen few of Athenian elites in fact  women ,slaves, poor etc couldn't even vote. 
So it can be said  
that modern democracy emanates from the French Revolution of 1789. Now many of the modern nation states, have made their constitution based on the French ideals. 
This was the first time that there was a claim of voting rights for all sections of the society. More importantly,

 ‘ Separation of power’ – by Montesquie.
‘ Social contract between citizens and the government’ – by Rouseau .
‘Ideals of social status based on merits’  etc were brought to light for the first time in the French revolution. And today, we know very well that these ideas are the very base and root of democracy.
The french revolution has a huge impact on liberal ideals which is the foundation of modern democracy and its functions and ideals. So it can very well be said that the “French revolution laid the foundation for the modern democracy.”