Yeah, rather than think "Vocaloid quality," just phrase it as "high quality results close enough to actual singing," because that's what you seem to want. A lot of Vocaloid things are made to sound, well, robotic, so it's hard to compare since there's so many different uses of them.
That being said, I'm gonna dump a lot of my favorite voice types on you (any videos will be in spoilers).
Renri's voice type sounds like it belongs in her late teens to early twenties, but can be used for lower ages too. Her lower range is really nice, but she's mostly a mezzo-soprano (leaning towards soprano range). I'd say her range is around A3~A5, based on having used her. She has a CLEAR bank, her normal bank, a WHISPER bank, and an EDGE bank. The EDGE only works with vowels, though, and is mostly for effects--literally an "edge" as you're starting a measure.
This one I'm biased towards because Hana's one of my all-time favorite UTAUs to use. Her voice type sounds like a mature woman, but can be argued for late teens still. She has a powerscale bank and soft bank, both being very well done, though you may sometimes need to change the pitches around if you're looking for certain effects (i.e. add something automatically assigned as "F4" on a note for A4 to "A4" if you're picky)
Another one I'm biased with because when I started writing, I used Mimi almost constantly. It's a great, easy to use bank, and there's even English CVVC and VCCV coming up. She has a Lyra bank, which is softer, a Lunae bank, which is more powerful, and old version banks. She's just great.
While I'm at it, I believe Mona Minarai's creator is pretty good friends with Mimi's, and has a great UTAU, too!
If cute banks are your cup of tea, Ami's probably for you. Though her arguably highest quality bank is Salad with a whopping 17 pitches, she's got a ton of other banks like Clear Cider, English (for Japanese users mostly though), a CV with 4 pitches, a 1-pitch VCV, and more. Did I mention she's adorable?
Kumi's another cute bank, but can pull off tons of different voices! She's capable of sounding really young and sweet but also mature and powerful and it blows my mind.
I should also bring some males in here too, huh?
I absolutely adore Kuri. He's got a great tripitch bank and his voice is a low-ish tenor, great for a lot of songs. If you're looking for males, give him a look.
Kiei's an absolutely crazy vocal and very unique and easily recognizable. His voice is really powerful and gives off a young man's voice. It's a young tenor and it just sounds great in general. Give 'im a listen!
Hakupo is a great bank. Unique like Kiei, and a little deeper. Not any deeper than tenor, but still a great bank if you wanna give it a listen!
I can't bring up Hakupo without also bringing up Mizuki because I love both of them with a passiona nd just li ste n to that vo ic e (also sorry for repeating the same song twice)
ALSO, some people that TUNE that you might want to look up because it looks like you want realistic results but it also depends on the person who tunes!!
(YouTube links)
kyaami
Though I used to be eh towards kyaami, she's gotten a lot better with tuning lately and the main reason I mentioned Renri in the first place was my friend heard her first from her. Much of the fandom will suggest kyaami to you, but I've got a load of other people if she's not your cup of tea, too.
R.K.
R.K. is one of my all-time favorite UTAU tuners, period. She's great with her UTAU and occasionally others' UTAU too. If you're not into her voice type, since she mainly uses her own UTAU, you may not like her, though she has some of the most realistic results I've seen.
PandaLolii
Though she doesn't have the MOST realistic tuning and isn't the most meticulous, she's still great, and if you want to stock up on USTs, she has tons.
Matt/Cheezits/CircusP
I feel like I don't have to say anything here lmao (though I know his tuning isn't everyone's cup of tea)
Macnspam
Also not the most meticulous, it's still great if you wanna give it a listen.
(Nico links)
Mingoashisaran
They use Meiji, Ritsu, Amaga Eru, just to name a few. They're really good, give 'em a listen.
Konuko
You probably heard about Meiji and thought she sounded realistic from Konuko's videos reposted onto YouTube. Konuko is very popular for making Meiji, Hakupo, Mizuki, and more banks sound great.
kaoling
More known as a Vocaloid songwriter, kaoling has done a few things with UTAU here and there and is fantastic with it, too. Check her out!
Ciel
They also mostly do Vocaloid/CeVIO (covers tho), but they've still done some UTAU work if you're interested.
TL;DR "Vocaloid quality" isn't a thing, and high quality VBs help but the people who tune them are even cooler ye ok lates B')