I just wanted to add to this thread by saying that EGA games at 320x200x16 on a true EGA monitor (in my case, I'm testing this with an IBM 7534, industrial version of the 5154) look substancially better than on a CGA/RGB monitor hooked to an EGA card. The "Specifications" section of the EGA Wikipedia article explains why, but all technical mumbo jumbo aside, it truly is noticible. Scenes in games have more "natural" looking browns, and sometimes some of these shades are lost in CGA. Some games that I thought had horrible 16 color graphics came to life on a true EGA monitor. These tests were made using the monitor mentioned above, and a Tandy CM-11, on a Tandy 1000 TL/2 computer.
Here's the excerpt from Wikipedia:
"The EGA uses a female 9-pin D-subminiature (DE-9) connector which looks identical to the CGA connector. The hardware signal interface, including the pin configuration, is largely compatible with CGA. The differences are in the repurposing of three pins for the EGA's secondary RGB signals: the CGA Intensity pin (pin 6) has been changed to Secondary Green (Intensity); the second ground of CGA (pin 2) has been changed to Secondary Red (Intensity), and pin 7 (Reserved on the CGA) is used for Secondary Blue (Intensity). If the EGA is operated in the modes having the same scan rates as CGA, a connected CGA monitor should operate correctly, though if the monitor connects pin 2 to ground, the shorting of the EGA's Secondary Red (Intensity) output to ground could conceivably damage the EGA adapter. Similarly, if the CGA monitor is wired with pin 2 as its sole ground (which is poor design), it will not work with the EGA, though it will work with a CGA. Finally, because of the use of the CGA's Intensity pin as Secondary Green, on a CGA monitor connected to an EGA, all CGA colors will display correctly, but all other EGA colors will incorrectly display as the standard CGA color which has the same values for the g, R, G, and B bits (ignoring the r and b bits.) Conversely, an EGA monitor should work with a CGA adapter, but the Secondary Red signal will be grounded (always 0) and the Secondary Blue will be floating (unconnected), causing all high-intensity CGA colors except brown to display incorrectly and all colors to perhaps (but probably not) have a blue tint due to the indeterminate state of the unconnected Secondary Blue."
http://en.wikipedia.org/wiki/Enhanced_Graphics_Adapter