It's in order of the seasons of Idol...they started with Kelly and ended with Lee.
Okay, so my reaction when I saw the tracklist for this compilation was that many of the songs couldn't be considered hits as the title suggests. I thought it might be false advertising lol. Of course, we all know BHC was a hit, and Kelly's Since U Been Gone was a hit, but I decided to look up the numbers for all of the tracks for comparison. For those of you that are interested, here's what I found (all chart data is Billboard). I hope this is okay to post!
Since U Been Gone - Certified Platinum, #2 on Hot 100, #1 Pop, #2, Adult Top 40, #22 Hot AC
Superstar - Grammy nomination, #112 Hot 100, #1 R&B
Invisible - Certified Gold, #37 Hot 100, #8 AC
When I See U - Certified Gold, Grammy nomination, #32 Hot 100, #1 R&B
BHC - 3 Grammy nominations (2 wins), Certified Multi-Platinum, #8 Hot 100, #1 Country, #6 AC, #9 Adult Pop
Takin' It To The Streets - #69 Hot 100
Home - Grammy nomination, Certified Platinum, #5 Hot 100, #1 Adult Top 40 and Hot AC
No Air - Grammy nomination, Certified Platinum, #3 Hot 100, #4 R&B, #2 Adult Pop
Light On - Certified Platinum, #17 Hot 100, #20 Adult Top 40, #23 Pop, #10 Hot AC
Live Like We're Dying - #18 Hot 100, #8 AC, #3 Adult Top 40, #10 Modern Top 40
Whataya Want From Me - Grammy nomination, #10 Hot 100, #12 Modern Top 40, #2 Adult Top 40
Sweet Serendipity - #38 Adult Pop, #96 Hot 100
One artist/song that should have been there:
Crush (David Archuleta) - 1.9 million sold, #2 Hot 100, #6 Hot AC, #15 Adult Top 40, #12 Pop
From the numbers, I guess some songs were bigger than I thought, and poor Taylor and Lee because their numbers aren't even a fair comparison to the other Idol winners.