It depends on what exact definition of talent we're using, and what counts as success, but for me there's been one entry that with what it brought to, along with what it achieved at the contest against all odds that stunned me, and that's Georgia 2016.
I love rock and lean very much towards alternative and independent rock. Eurovision is just about the worst place in the world to come for that kind of rock. Poser pop rock is pretty much all the contest attracts for various reasons. Young Georgian Lolitaz were the opposite of what's deemed acceptable for a contest like this and they were trashed by ESC fans from the get go. Meanwhile a select few of us were getting really excited for this rather rad internal selection. An actual alt-rock band were going to Eurovision with a cool track that wasn't made to please or meet standards of what people think an ESC song should be. They were however pleasing a side of my taste that doesn't compute with our beloved contest. Eurovision has always been my sugar fix and I don't hide it. I never thought i'd hear music this "good" at the contest that wasn't a chamber pop ballad or something along that line (cause boy, Eurovision does on occasion satisfy that side of what I love at least). "Midnight Gold" was dirty, fuzzy psych-rock and it made no apologies for it.
Not only all this but they somehow came with what I thought was the best performance of 2016. For any band that takes themselves half seriously, faking your instruments is a big problem but they handled it in such a zany way. I don't know if i'll ever see something as cool at the contest again, that just worked as well as it did. They came 20th, which is not high, right? Correct but I consider it a humongous achievement considering what they were bringing and the crowd they were bringing it to. As an added bonus they beat that pop rock band by a place. Young Georgian Lolitaz prevailed because they weren't supposed to make the final, at least according to a large chunk of fans. For me it's my favourite moment of "talent prevailing", and it gave me a huge pleasure moment that year.
Two other examples (prevailing in the highest sense of the word):
2016 Jamala - 1944
2017 Salvador Sobral - Amar Pelos Dois
You can have technically the most impressive vocals ever, but talent for me is worth nothing if there isn't something behind the voice and I don't feel
it truly. Those two winning entries above were exceedingly rare moments when the most deep and impassioned performances actually somehow won. I can't also reply in this topic without mentioning "Suus" and Valentina's legendary "Maybe" qualification. All the songs I mentioned here I believe had the full package: charisma, uniqueness, nerve and talent. I'm just devastated Sofi Marinova was a flop cause queen needs to be added to this list of people.