Gullivers first two voyages are stories of misfortune rather than stories of adventure

Are you looking for evidence to prove this statement? If so, Gulliver had the misfortune of being in a shipwreck during his first voyage..... none-the-less, he was the sole survivor. Thus, his misfortune really wasn't misfortune for him at all.

We can look at his interactions with the Lilliputians in the same way.... they held him captive, yes, but he also allowed them to hold him captive. When he signs the contract that frees him from his captivity, neither the contract or the captivity are misfortune, as he always has the strength and power to overcome the situation. Gulliver is simply a peaceful man.....

In Part II, Gulliver has the misfortune to sail on another voyage plagued by bad weather. Although, in Brobdingnag, the tables are turned and rather than being the one with power.... Gulliver finds himself at the mercy of giants. Once found (he yells as he's about to be stepped on), Gulliver is treated like a toy... but not mistreated (unless you count the dwarf).

As to your question, Gulliver's adventures are directly related to his misfortunes, and the two together make up his stories. I believe the first two voyages qualify as tales of misfortune and adventure, not simply one or the other.