Don't Stop The Way You Are (Journey vs. Bruno Mars vs. The Killers)

Journey – Don’t Stop Believin’ (instrumental)
Bruno Mars – Just The Way You Are (diy acapella)
The Killers – Spaceman (acapella)

Waiting For The Stars (Linkin Park vs. Hum)

Linkin Park – Waiting For The End (acapella)
Hum – Stars

I Melt With Adam (Blink 182 vs. Modern English)

electric version!

Blink 182 – Adam’s Song (instrumental)
Modern English – I Melt With You (acapella)

I Melt The World Away (Modern English vs. Oasis)

acoustic version!

Modern English – I Melt With You (acapella)
Oasis – Half The World Away (instrumental)

New Catalyst (U2 vs. Linkin Park)

U2 – New Year’s Day
Linkin Park – The Catalyst (acapella)

I Like California Gurls (Nada Surf vs. Katy Perry vs. Leona Lewis)

Nada Surf – I Like What You Say (instrumental acoustic guitar loop + original)
Katy Perry – California Gurls (acapella)
Leona Lewis – Bleeding Love (acapella)

We're Livin' In (d)Anger

here's an excellent video done by leemaven.

John Lennon - Imagine (instru + original)
Aerosmith - Livin' On The Edge (acapella)
Oasis - Don't Look Back In Anger (acapella)