Willempie,
I agree with you. The French is one of the sharpest, most dynamic of the "semi-open" games. 8)(I use Karpov's definition of semi-open, 1.e4 vs anything but 1..e5 but I realise there are many transpositional possiblities.)
MNb,
The similarities between the French and QGD apart from the pawn moves (excuse the descriptive notation) P-K3, P-Q4, P-QB4, go much more than skin deep. The Tarrasch variation can lead to very similar positions, whether you are discussing the French or the QGD.
The differences are important.

The extra tempo allows White to develop his problem Q's Bishop (again, excuse the descriptive, but it has its purpose here) outside the pawn chain. Also, White doesn't have to worry about P-K5. Yes, these are distinctions, but ones that serve to remind the French player just how actively White has to play against the French to achieve anything more than equality. 8) The similarities have been sufficient for such players as Korchnoi, Mikhail Gurevich, Botvinnik, and other top players. I guess it's just personal preference whether to focus on the similarities or differences in openings.