1920 x 1200 resolution monitor with VGA not detected by Mac OS X 10.7.2
You are unlikely to be able use the VGA input to go above 1080p

But just to make sure follow this answer how to view more Resolutions to try with.

MacBook Pro with Retina display (Late 2012) not outputting anything above 1080p

Select the monitor in System Preferences:

System Preferences -> Displays -> Monitor(not Built-in Display) -> Display Tab -> Resolution 

Change from 'Best for Display' to 'Scaled' whilst holding the 'alt' key, more resolutions will be listed for you to select, 

As noted in the comments, you have to start in the default mode 'Best for Display', and move into 'Scaled' whilst holding the alt/option ⎇ key, not the other way round