RAW Main Eventers/Upper Midcarders:
Heels:
Triple H
Shawn Michaels
Chris Jericho
Kurt Angle
Edge
Carlito
Gene Snitsky
Faces:
John Cena
Kane
Big Show
Shelton Benjamin
Rob Van Dam
SmackDown Main Eventers/Upper Midcarders:
Heels:
JBL
Christian
Randy Orton
Eddie Guerrero
Orlando Jordan
Muhammad Hassan
Faces:
Batista
Booker T
Chris Benoit
Rey Mysterio
Undertaker
(Please tell me if I've missed someone)
Where does Brock best fit? The RAW Faces look the weakest, with only Cena that's a 'real' Main-Eventer, so that's an option. But, CM Punk is said to be debuting as a Main-Event face on RAW. I haven't included Hogan on the face list because pretty soon he'll have another 'last' match and leave again.
But SmackDown! could really do with a mega-draw. Brock Lesnar was recognised as 'the man' in this company (along with HHH) so putting him on Smackdown would do wonders for the show, but if you were to put Lesnar on SD, you need to turn another RAW Main-Eventer face (Angle or HHH) and push Kane, Show, or Benjamin up to Main Event level. Now that Benjamin is not the IC Champion, that gives him a perfect oppurtunity to take the step-up and feud with some credible main-eventers (I'm thinking HBK after Hogan's gone, HBK V Shelton II

).
So yeah, where would you put him? I'd put him on SD personally (as long as we see face-turns and pushes and CM PUNK

on RAW)