Someone may find this via google and find it handy:

Tested on a 360 elite (new on xmas 2008) with all the updates (up to and including the NXE) using a 19" Dell non widescreen LCD monitor at 1280x1024. Actual play NOT thoroughly tested, just booting.

Dont work at all:

Conflict: Desert Storm 2 (I think its called back to baghdad in the US?)
James Bond 007 - From Russia With Love
Operation Flashpoint: Elite
Conflict: Vietnam
Fallout: Brotherhood of steel
Conflict: Global Storm / Conflict Global Terror (UK/US)
Far Cry: Instincts - Evolution (Oddly, the original runs really well and on VGA)
Metal Gear Solid 2 - Substance
Project: Snowblind

Works on 360, but not with VGA:

EA Sports rugby 2006
Halo 1 (Will work fine if you start it with component, get the update, then run it on VGA)
First to fight
Conflict Desert Storm (1)
Return to castle Wolfenstein (Oddly, *parts* seem to work on VGA)
Unreal Championship
Commandos 2: Men of courage
Splinter Cell
True Crime Streets of LA
Ghost Recon 2
Raimbow Six 3

Works fine on 360 with VGA:

Shellshock - 'Nam 67 (looks good but draws a black border????)
Max Payne
BLACK (Looks nice on the 360 but somehow doesnt seem the same???)
2006 Fifa World Cup (looks a bit pixelated)
Goldeneye: Rogue Agent
Tony Hawks Underground
Halo 2 (get the latest update to fix some VGA issues - looks NICE on the 360)
Splinter Cell 2 - Pandora Tomorrow (Graphics seem crappy?)
Full Spectrum Warrior (looks a bit pixelated?)
Without Warning (actually looks really nice on the 360, shame its a bit of a pants game lol)
Far Cry: Instincts (looks nice! - Instincts: Evolution is NOT supported at all)

By the way, these are for the PAL versions.
Most of the games which i say work, but not with VGA *probably* WILL work using the US/Japanese (NTSC) versions (they are primarily 60hz which is vga-friendly whereas the 50hz PAL standard isnt)