I only play on sites that are at the intersections of several different biomes (both stones and wildlife) for variety, in 4x4 areas. 3 different biomes is a minimum, 4 is ideal, 5 is so rare I have given up finding one. One of the biomes must be a mountain (hey, I play dwarves, not humans !). And I want to have all 3 types of stones (white, grey, black): usually not a problem if there are 4 different stone biomes in the embark area.
Maxing out the variance is the world gen parameters helps a lot with that. Also, I like the biomes to be wilderness or untamed wilderness.
Infinite fresh water is a must: preferably an aquifer, but I'll settle for a river. Even a temperate/cold wet biome (e.g. marsh) will do, since freezing water replenishes in winter, and wet biomes have lots of pools so it's close enough to infinite.
Sand is also a must, as is flux. And to be honest, on maps with 4 biomes, it's not hard to get.
Magma is on every map if digging deep enough, so I don't play on volcanoes.
I am currently playing on a map with 4 stone biomes that are so close to each other that my fortress is straddling all of them, so I have lots of different stones , metals, and gems. 2 of those wildlife biomes are identical, but it is still 3 different wildlife biomes (for zoos). Only one of the biomes has an aquifer. So I am very happy with it.