The French heavy and medium tanks were definitely superior to the PzII and PzIII technically. As Forczyk writes, "If any word describes the state of German tank design at the start of Barbarossa, it is mediocrity". And this is Barbarossa, before the 50 mm of front armour for the latest designs, before a 50 mm gun in the PzIII. Both the PzII and PzIII at the time had enough armour to resist rifle caliber armour piercing bullets. Only a handful of PzIIIs with 30 mm of armour were available, but even 30 mm was not enough to withstand fire from French 47 mm anti-tank guns or newer 37 mm guns on light tanks.

Against them, the French tanks appeared absolutely titanic. The Char B1 bis had 60 mm of armour, the S 35 had up to 47 mm. On paper, in a one on one duel, there was absolutely no contest: a German medium tank would be demolished by a French medium tank.

However, the issue is that tanks don't fight in one on one duels. For 400-odd Char B1s and Somuas, the French had thousands of Renault R35 and Hotchkiss H35 tanks, in addition to absolutely ancient Renault FTs still in service. The majority of these tanks were armed with the low velocity SA 18, which could not even pierce 14.5 mm of armour of the early PzII or PzIII variants. The 30-40 mm of cast armour of these light tanks may have been impressive, but the low quality mean that a thorough pounding by a 37 mm gun would still knock them out.

The other German trick was that those 37 mm guns weren't only on tanks. The German tank units weren't made up of just tanks, but also infantry and anti-tank artillery that were trained for combined-arms action with tanks. In comparison, French tank tactics were not as advanced and the budget-conscious French military skimmed on the combined-arms exercises. The result was rather poor for the French.

B1 tanks did put up an impressive fight, for example at Stonne, where Pierre Billotte's tank took 150 hits (none penetrated) and knocked out 13 tanks in return. Unfortunately for the French, the B1s couldn't be everywhere at once.

R. Forczyk, Tank Warfare on the Eastern Front 1941-1942

M. Orlovskiy, Medium Tank Pz.III Sd.Kfz.141

Y. Pasholok, Less is more http://warspot.ru/6356-menshe-da-bolshe

A. Ulanov, Ye. Belash, Stonne 1940 http://tankarchives.blogspot.ca/2015/06/world-of-tanks-history-section-stonne.html

In adition to what u/TankArchives has informatively stated:

There are a number of "softer" factors in the French tanks that puts them in a disadvantage against their German counterparts.

• The French tanks usually have a lower power to weight ratio, usually 7-10 hp/ton vs 11-17 hp/ton of the Germans. This translates into the mobility aspect, with the Panzers being more suited to conduct more mobile operations.
• The French tank force had an abundance of models sporting a one-man turret. This increases the workload of the commander immensely. Try to picture yourself in the turret seat of a Somua S35: on paper you have perhaps the best tank the French industry can supply you with. Armor, firepower and mobility under your control. But in reality, your task in a ingrateful one. You must command your own crew; you must spot the enemy threats and asses them; you must aim and fire the gun; you must load the 47 mm shells, weighing several pounds, in a very cramped turret. All this, of course, impacts the overall performance of the tank as a whole.
• The French didn´t have as much radio sets as the Germans in their tanks. Fluid communications make critical information flow quicker; reaction time to threats is diminished (ie, if one tank spots a concealed AT emplacement and has the means to communicate it, then every tank in the unit is aware of the threat) and oportunities can be exploited more easily. Manouvers can be better organized and controlled.

As a little extra, here is a little video that nicely summarizes Billote and his crew´s exploits in their B1 bis: https://www.youtube.com/watch?v=rBdOp4Btfrg

D. Lehman, Number of AFVs on 10th May 1940

Edit: formatting and sources added.