I think it´s wrong to leave a culture before having experienced it at literally every hour of the day... which I have done in Paris. I can´t say which is my favorite... things are a little fuzzy when I try to find my way back to my bed at 4-6 a.m., but I love the hours right before then. I also like the afternoon/evening... 2 different crowds, both captivating. And of course, night is when the city truly becomes the "City of Lights", a name for which it is so famous... Mornings are a little slow, but a good espresso helps shake off the post-night fog. And it can be quite entertaining to watch the store owners open up their shops. I would probably enjoy the Parisian mornings more if I didn't have to wake after only a couple hours of sleep and run through muddy streets to catch the metro and make it to class on time, rainsoaked and cold...
But sleep is for the dead.