LOL at the thread title.
I only watched IDA, but I can't pick a top performance

Can I have a few please? Yes? Okay.
These aren't in order!
Sarah - Midnight Train To Georgia (my current favourite

)
Sam - Defying Gravity, Anyone Who Had A Heart, I Love Rock n Roll
Niamh - Wind Beneath My Wings, Don't Speak
Fran - Somebody To Love
Sarah and Rachel - As If We Never Said Goodbye
Sam and Rachel - Memory
Niamh and Rachel - Another Suitcase In Another Hall
(And I wasn't even a Rachel fan!)
Olivers - Electricity, Give A Little Love, I Have a Dream, Tomorrow
Group Performances - NEVER FORGET, Who Will Buy, Good Morning Baltimore, Things Aint What They Used To Be, I'd Do Anything (the first one), Dancing In The Street
That's quite a lot, kind of defeating the object of the thread here