1/ Mika- "Ain't Got No I Got Life":
Notice in the comments several people declaring that this is better than the original.
I used to like Mika, but this version is a failure. Here's why: the song is clearly cut into 2 parts, the 1st one is sad, with a kind of sadness bordering on despair, the 2nd one is hopeful, because there is a humorous touch and because "the speaker" asserts her freedom and love of life and will to live. From "What have I got", there's a noticeable shift in Nina Simone's singing- before, she brings pain, anger and resentment into her voice, afterwards, as she declares that despite lacking all those things she still has things that can't be taken away, especially life and freedom, she becomes animated, passionate, spirited. I don't see that in Mika's performance. He's happy and cheerful throughout all of the song, which clashes terribly with its spirit (though I should note that it's also the band's fault, not only his). The whole point is lost. This is a hopeful song, but not a happy one. Mika's performance is thus light, shallow, superficial.
2/ Christina Aguilera- "At Last":
"At Last" is also covered by Beyoncé:
This is the most famous version, also my favourite:
The talent of Christina Aguilera and Beyoncé is undeniable, but in this case Etta James is much superior. If there's something lacking in Beyoncé's performance (feelings, I mean), Christina Aguilera, much as I admire her and like some of her songs, completely ruins "At Last". She focuses too much on showing off her voice and drawing people's attention to what she can do with it, that she destroys both the melody and the emotions of the song. I listen to music not to be impressed by singers showing off their vocal abilities. Singing should be about expressing, not impressing. Thanh Lam, Sam Tsui, a former classmate of mine named V, those American Idol/ The Voice/ [Britain/ America...]'s Got Talent contestants...- they all ruin music without knowing it.
This leads to another topic: melisma (http://www.seattletimes.com/entertainment/wo-o-o-whoa-stop-oversinging/). Whitney Houston is 1 of the few singers who bend and stretch notes and do "vocal gymnastics" without sacrificing the song. She does it naturally, unaffectedly, and still has feelings. Most can't do so.
3/ Another example of oversinging- Claudia Rose performing "Misty Blue":
Here is Dorothy Moore's version:
My favourite is Ella Fitzgerald's version:
There is more melisma in Dorothy Moore's version than Ella's, and when Claudia Rose sings, she abuses it so that not only does she lack emotions but the melody is no longer recognisable. Other people like this, perhaps. I don't.