My favourite is Une Enfant du Siècle and it is also the only album where I can't really decide which is my least favourite song. I think a lot of people fooled themselves that they liked it when it first came but I've always loved it. Mes Courants Électriques was my favourite album before UEdS.
There's already a thread like this one here but it only lasted a couple of days around the time when UEdS had been released.
Edit:
Going to add my list here also...
1. UEdS
2. MCÉ
3. Psych
4. Gourm