So as far as reordering this list from alphabetical per rating to overall difficulty, I'm not sure how we'd go about it. Some ideas:
a) Grab the ps3t ratings, sort by that (tedious, unless you can script it)
b) Users vote up/down (might take a while to stabilize list)
c) Everyone list their plats by relative difficulty, and we go from there (will take a while to get big picture, uncertain 2nd part)
For one, in case we go with c), I'll list my games by my opinion of difficulty (time is factored in, less weight than actual difficulty), high to low. Of my games, I'm at 28% on Resistance 2, so that's omitted. I don't have the Vanquish (91%) and inFamous 2 (54%) plats, but I've included them anyway since I feel I have a good idea about their difficulty.
Gran Turismo 5
The Beatles: Rock Band
GTA IV
Cross Edge
Wipeout HD
Vanquish
Yakuza 3
Rock Band 2
Final Fantasy XIII
Modern Warfare 2
Resonance of Fate
MLB 09 the Show
3D Dot Game Heroes
MLB 11 the Show
Yakuza 4
Dragon Age: Origins
AC Brotherhood
Bioshock
Ferrari Challenge
Mass Effect 2
Uncharted: Drake's Fortune
Uncharted 2: Among Thieves
LittleBigPlanet
Katamari Forever
inFamous
inFamous 2
Assassin's Creed II
Enslaved
Ratchet and Clank: A Crack in Time
Portal 2
L.A. Noire
Prince of Persia
Heavy Rain
Prince of Persia: Forgotten Sands
Note that we had a discussion about Wipeout HD recently... I rate GTA IV and Cross Edge are above it because of time (150+ hours each).
edit: moved Katamari Forever up