Let's try IGN.
I won't count downloadables.
PS3
1) Metal Gear Solid 4: 10
2) Resistance 2: 9.5
3) Little Big Planet: 9.5
4) RaC: Tools of Destruction: 9.4
5) Ninja Gaiden Sigma: 9.3
6) Uncharted: Drake's Fortune: 9.1
7) Resistance: Fall of Man: 9.1
8) Valkyria Chronicles: 9.0
9) Folklore: 9.0
10) Buzz! Quiz TV: 8.9
Average: 9.28/10
X360
1) Gears of War 2: 9.5
2) Halo 3: 9.5
3) Mass Effect: 9.4
4) Gears of War: 9.4
5) Left 4 Dead: 9.0
6) Prey: 9.0
7) Dead or Alive 4: 9.0
8) Forza Motorsport 2: 8.9
9) Fable II: 8.8
10) PGR 3: 8.8
Average: 9.13/10
Wii
1) Super Mario Galaxy: 9.7
2) SSB Brawl: 9.5
3) Metroid Prime 3: 9.5
4) Zack and Wiki: Quest for Barbaros' Treasure: 9.0
5) RE4: Wii Edition: 9.0
6) Super Paper Mario: 8.9
7) Skate It: 8.5
8) Mario Kart Wii: 8.5
9) Trauma Center: New Blood: 8.5
10) Wario Land: Shake It: 8.4
Average: 8.95/10
So, the PS3 has the best, non-downloadable exclusives according to IGN. Sorry if I missed anything.
(Former) Lead Moderator and (Eternal) VGC Detective 
