Are lizards the best adapted animals to live in desert

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I don't know if they are the "best" adapted but they certainly are better than amphibians, snakes, turtles, birds and most mammals in their ability to survive in deserts. That may be because they are diapsid reptiles, and diapsid reptiles (which include the ancestor of birds, crocodilians, dinosaurs, and snakes) appeared to have evolved to adapt to arid conditions during the Permian, when all the world's continents were joined together to form a single super continent known as Pangea. Since coastal areas were reduced, much of interior the world turned arid due to lack of moisture rich air currents from the oceans. Diapids evolved to secrete uric acid to save water, even though their ancestors secreted urea, which requires more water to get rid of.

Insects, however, may be just as good, as they too secrete uric acid. Lizards are small enough to burrow into the sand or scamper into an underground burrow to escape the heat when it gets too hot. The desert iguana, a lizard, can tolerate a higher body temperature than just about any vertebrate, higher even then the desert adapted camels. There are also more species of lizards in deserts than there are amphibians, mammals or snakes. Snakes are less tolerant of high temperatures than lizards, which may have something to do with their evolutionary origin as marine reptiles. Nevertheless, there are some mammals, such as the kanagroo rat, which are also superbly adapted to deserts, but they have to be active at night to keep themselves from overheating.

This is a question right up there with the ol' "Who would win in a fight between a lion and a tiger."

The simple answer is that any organism (plant or animal) that survives, grows, and reproduces in a desert environment (and there are many different desert environments) is well adapted to that desert environment.

Uh-huh!,,and so are camels, wild onagers and scarabs/dung beetles.