well it depends.
1. Production. Hills are always good. It doesn't matter if it is a desert, tundra or grassland hill. It always gives you good production for less food. Same for forests. Well I don't think you get forests in desert, but in tundra you will have plenty of them.
2. Food. Sometimes you have an oasis or two in the desert, which is a good tile that doesn't need to be improved. However, it is highly important to have a river. No river = don't settle in desert in the most cases. With a river OTOH you have a lot of flood plains that give you a nice food amount. In tundra you may get food from the sea or from deer.
3. Resources. Even tundra or desert terrain can make up for a good start, if you have enough resources at hand. In tundra you get a lot of deers normally. Plus: a tundra city is very likely coastal. Fish or whales resources can give you food an gold as well. In desert you may have an oasis or if lucky, several copies of incense.
4. Do the math. How large do you want your city to grow? Just look how many "good tiles" you have there. Several floodplains/deer plus several forests/hills? If you have enough tiles that deliver production and food, you may want to settle there.
Pure flatland tundra or desert without a river is almost always a bad idea.
EDIT: uploaded a screenshot from my game to show a good desert city with resources and river