#1 would be Ice Biome, it's not the most difficult biome and it's hard for corruption crimson or hallow to take over (besides when you first enter hard mode), the aesthetic and all that junk, i like the color white, it's sleek, it looks good, and it complements black and blue, two of my other favorite colors... I often end up making a lot of good and high quality builds using ice biome materials
#2 Space biome, ohh clouds, and sunplate blocks, it's one of the more difficult biomes but i like it reguardless of how lacking in content it is, building you're own space bases are fun as well as fending off against wave after wave of harpy and wyvern with friends (but sucks without them), as well as some of the benefits of low gravity and some of the fun you can have
#3 Now this is a hard one..... probably ocean biome because of palm wood's look as well as since most of the angler and ocean stuff was introduced in 1.3 it all has good sprites that all synchronize with that ocean look