Here's the confirmed tracklisting and cover for the Greatest Hits according to EMI:
01 Wannabe
02 Say You'll Be There
03 2 Become 1
04 Mama
05 Who Do You Think You Are
06 Spice Up Your Life
07 Too Much
08 Stop
09 Viva Forever
10 Let Love Lead The Way
11 Holler
12 Goodbye
I read somewhere before that it was going to have unreleased tracks, B-Sides, and such, but I guess this is all we get. Every single one of these has been on one of their three albums, and I already own all of them. This is rather disappointing. Way to not aim for the fans...