Figured I may as well update this since my taste has changed... Significantly. Only choosing VOCALOID vocals is suffering too so I'll throw in some SynthVs.
English: Eleanor Forte
(Synthesizer V)
Considering how
good her lite vocal is her pro version will easily be one of the best English vocals full stop. Also, I really love her tone, it's what I wanted from Cyber Diva but didn't quite get. Coincidentally Cyber Diva is my favourite English VOCALOID right now.
Japanese: Mew
(VOCALOID3)
God, why did I even say Haruno Sora? That's recency bias for you, baybee. I love Mew's voice provider (
Miu Sakamoto, everyone), and her tone is just gorgeous. All I wish is for her to somehow get an update with a more full low range like her voice provider, otherwise she's perfect. Shout out to Galaco also!
Chinese: Cangqiong
(Synthesizer V)
Surprising absolutely nobody. I'm a huge fan of Cangqiong, her design and voice are perfect. She has insane range, versatility and depth that I didn't even thing would be possible. If it has to be a VOCALOID, I still love Mo Qingxian and am partial to Chuchu.
Korean: UNI
(VOCALOID4)
This still hasn't changed. She's a little funky but I adore her tone and think she's great for poppy stuff. I always regret that her appends and subsequent English vocal couldn't be released.
Spanish: Bruno
(VOCALOID3)
I still love MAIKA for her versatility but Bruno is just... amazing. I'm not normally a fan of male vocals but his quality is bonkers, and his tone isn't half bad either. Not much to say because I don't care too much for Spanish vocals but that's what I feel right now.