I'm not sure where you got your information from, they had some of the best tanks in the world, and many were better than their German counter-parts. However they also three major downfalls compared to the German tanks.
1). They had no radios, which meant that communication was very difficult.
2). The French commanders thought of them as Infantry support, and so instead of being concentrated in Tank divisions like the German tanks, they were spread out way too thinly in Infantry divisions and so could do very little.
3). The Germans owned the air, even with help from the RAF, the French Air force was poorly led and was just generally useless, when they lost the fight in the air, the tanks were left with no air cover and so were sitting ducks to the Stukas and other German aircraft.