One of the features I would like to see is the video resolution of the game given in the game description. Might save downloading or giving a bad review to a game. With todays hi res 20 inch plus widescreen monitors any EGA game is almost unplayable and even the VGA are not much better. Many of these games were also released on the Amiga and Atari ST (wonder how many STs Dungeonmaster sold) and better downloaded from an abandonware site and played on an emulator.
I also noticed several people asking about changing the window size of a windowed DOSBOX. Inside the files of every game is a shortcut to
Launch Graphic Mode Setup

open this and you get a window with the basic settings. Select the Advanced settings you can now select to kee the Aspect Ratio stops the wide screen streching the scaling engine and the window resolution.
Play with the various scaling engines as some suit some games better than others.

If you want to know what resolutions any game supports, you can go to a place like this one: http://www.wsgf.org
It tells that and also how to modify some resolutions and aspects to support modern screens, if that's possible.

I believe most games here can be played in windowed mode, but properly controlling the mouse can be a chore sometimes. Still, in the games' forums you can find high res patches and that kind of stuff.

Playing strategy games in windowed mode, in specific, is the worst. Trying to hit the edge of the window just right in order to scroll and all.