First of all, love the idea of this site. So many great games are just a plain hassle to install and tweak to work well on modern PCs. My question though is if these offer widescreen support? for whatever reason my monitor flickers and makes games that are at like 640 x 480 resolution.

A lot of the older games are at fixed resolutions: 320x200,320x240,640x480,800x600 (And I think Sacred is locked to 1024x768). Due to the lack of 2d/3d hardware, and hud/gui design.
You can check out places like Widescreen Gaming for a good list of max windscreen sizes and support. (Anyone know any others?)
Depending on your video card, you can set the game to play @ 4:3 in the 16:9/10 window. Update to the newest drivers if you have not already done so.

Your monitor may also have a specific function for this. I know mine does. I too prefer to play 4:3-only games in a 4:3 aspect ratio. It looks stupid when the image is stretched out to widescreen, especially if it's a lo-res image to begin with. So I play those games with a black bar on each side of the screen.

It might also be a refresh rate issue, I used to have a program called I think Refresh Lock, it may well make no difference but it's free and might be worth a try
I doubt an LCD monitor would be going that strange but you never know. The reason I was using it was that my 17"crt at the time squealed like a pig being improperly fondled every time the refresh rate dropped to 60hz so it gave me quite a headache to play icewind dale. Then again this same monitor exploded and began to belch black toxic fumes a few months later so I suppose it should have been a warning sign...

When it comes to refresh rate on LCD, values higher than 60 Hz (or any native value a monitor has) can cause problems (more blurred picture than one would expect). That doesn't change the fact, that low resolutions will simply look bad no matter what you do :/
Games shipped with dosbox should be easily tweakable to work on native resolutions (with or without correct aspect ratio).

Now that's a mental image I could have done without :P
OP - you can also check for mods for a particular game which allow for widescreen support - I found one for Fallout 2 and it looks much better now.