I like maps that are civ-specific (i.e. Egypt as a river civ surrounded by desert, Russia by lots of forests, lakes, rivers, and tundra, etc.), however I agree with other posters that a hilly map is a good one. Mountain ranges are great too, at least early on, to create a barrier from aggressive neighbors forward-settling me, and to block waves of barbars.
Also, I tend to look for a variety of luxury resources when founding cities, especially since the happiness/amentities changes between Civ5 and Civ6 (I tried the Colloseum route, and I wasn't convinced the opportunity costs were worth the ED+Col). I am a tall player, so I really only need a handful to keep my cities happy, if not ecstatic. Stone, horses, and iron are always priorities too, and always fresh water!!!