In terms of GI, the Glycemic Index, sure they are. However, the more important measure it GL, the Glycemic Load, which is basically the GI multiplied with the average amount.
For example, even though a cherry has much higher GI than a potato, you eat more sugar/carbohydrates in one potato than in one cherry, so a potato has higher GL and thus higher insulin response.
How many people would think to compare a single cherry to a single potato though? Most people would think in terms of roughly equal mass (x grams of cherries vs. y grams of potatoes where x is approx. y).
For example, even though a cherry has much higher GI than a potato, you eat more sugar/carbohydrates in one potato than in one cherry, so a potato has higher GL and thus higher insulin response.