In terms of Brands, many have had good success on this forum with the following:
Billabs -
http://www.billabs.comHapp Controls -
http://www.happcontrols.comNieman Displays -
http://www.niemandisplays.comBetson Imperial -
http://www.betson.comI have heard bad things on this forum with Wells Gardner (newer models), Makvision, Pentranic, and ALS Marketing. As such, I would avoid them.
Next you will need to know some other things:
Standard Res (CGA) - 15Khz
Medium Res (EGA) - 25Khz
High Res (VGA 640x480) - 31Khz
SVGA (800x600) - 38Khz
XGA (1024x768) - 48Khz
Please consider the modes of which games you will be using. Many raster arcade games run at CGA res. There are some that run at EGA and a few others that run at VGA res. Most vector arcade games look better at XGA or even higher res. It is best to consider the modes a monitor can display before buying it. Driving too high a resolution to a monitor can damage it permanently. If you want to run at lower resolutions natively, you need a video card that can output at lower resolutions such as the ArcadeVGA.
There are some monitors that can handle multiple resolutions. For example, Nieman has a tri-sync that does CGA through VGA res. Betson makes one that goes up to SVGA. Billabs makes one that does CGA through XGA. Monitors that are analog are simpler design which increases reliability, but at the drawback of having to manually adjust when you change resolutions. Digital Monitors automatically remember settings, but it means more parts and sometimes they are less reliable.