The monitor would intermittently lose the video signal every 30 seconds and the graphics became slightly blurry. A power-cycle fixed the issue but I'm interested if this has happened to anybody else over VGA?
That sounds more like the xbox misbehaving when you mentioned the 'blurry' part. I used VGA on my monitor for 6 months with no problems. Now I'm using component on a new 28" monitor due to input restrictions.
If you start getting odd visual irregularities (green tinges, 'pixelation', black bars etc) then that would indicate the GPU is up to it's usual tricks – overheating.
Check to see the adapter is securely plugged is a start.
Also do the graphics for other games get better than Saints Row?
Grid
PGR4
GTAIV
Kameo
Assassins Creed
DBZ Burst Limit
Ninja Gaiden II
+ heaps of games with better visuals
All have better graphics. Also make sure you adjust the display resolution. You could be playing in Standard definition which will flatten the experience a lot!