I just said, not Boot Camp. I don't have any Windows discs lying around that isn't used.

The problem with *nix ports is that they're often done by different teams and would require additional licencing and that'd just make it too cost prohibitive.
I'm not sure you'll be able to play Unreal or anything that needs full 3D acceleration but something old & crappy like duke3d should probably be emulated pretty well.

The DOS games (Duke Nukem 3D, Rise of the Triad, etc.) are emulated through , which is also available for the Mac and other platforms. However, you will need access to Windows or a Windows API implementation (such as [url=http://darwine.sourceforge.net]Darwine) in order to get the files out of the GOG installers. Once that step is done, however, just replace the Windows version of DOSBox with the OS X build and you're all set.
As for Windows games, I'm not sure. I haven't used Parallels so I don't really know about its speed. Another option is VMware Fusion, which can run even modern 3D games like Oblivion. Fusion has a 30-day trial available so you can give it a good test drive before you make up your mind. Note that Fusion requires an Intel CPU; if you have a PowerPC it won't work. Any Mac from 2006 or later has an Intel CPU.
Whatever option you go with, don't bother running the bundled Windows version of DOSBox through any sort of virtualisation even if it works; the native Mac version will give better performance and will be much easier to work with in the long term.

As for Duke Nukem 3D, there's a Mac OS 9 release by MacSoft, an "official" Mac OS X release floating around in the Internet compiled for PowerPC, and EDuke32.
On my really old PowerBook (G3 400, Rage Mobility 128 8 MB), EDuke32 is dog slow (it seems to use software OpenGL rather than harnessing what little power the Rage Mobility 128 offers), so I have to use the "official" PowerPC port with a bit of trickery to get it to use the Duke3D Atomic data from the GOG package. (Using DOSBox wouldn't be practical on PowerPC systems because x86 is rather difficult to emulate.) However, for an Intel Mac, EDuke32 would probably be very feasible.

I use Crossover Games (WINE) to run Steam and GOG games on my Mac.

You say not to say bootcamp but if you want consistent frame rates and best compatibility then it's the only answer.
Virtualization (VMWare or Paralelle )is a hit or miss some will run correctly (as long as you have a pretty powerful computer) but a lot of other will either refuse to start, crash randomly or work but with terrible framerate.
But if you say you don't have any Windows disk around then virtualization if out of question anyway.
Other solution like Crossover often have better performance (than virtualization) but with worse compatibility.
No honestly if you realy want to play on your Mac with maximum comfort and compatibility then invest into a OEM Windows license and go with bootcamp.

parallels, i've used it to play tf2

I thought that other members might be interested in knowing that you can use these games on an i.Mac - "Stonekeep - Beneath a steel sky". I used Fusion to install WinXP into my iMac 'needed to run office', and much to my amazement the games I have downloaded work perfectly with no loss of performance. Its possible that others work but these are the ones I own so far. Perhaps somebody could list some more that work with the iMac-WinXP combination.

I bought the Freespace library and it runs very well with FSOpen. I also had Descent: Definitive collection and I use it through D2X-XL. Nice native options.
However, even some old games are horrible in Fusion. Virtual Pool 3, for one example. The mouse is almost uncontrollable. Descent 3 is no good either.
I've been able to run TOCA 3 fine in Fusion, but when I reboot into Boot Camp it just seems a bit nicer. Like the controls are a tiny bit better.
For something like Supreme Commander - forget about it. Just reboot.

Note that you can replace the Windows versions of DOSBox and ScummVM with the Mac versions and run the titles natively. You only need to use virtualisation for actual Windows games.

Many thanks to Arkose for the information, being fairly new to th iMac I have yet to discover the extras that can be used with it.

Hi there,
Being an old PC user turned Mac I as well find myself sometimes want to enjoy some old goldies.
For Windows games, Crossover Games or true emulation like and [url=http://www.vmware.com/products/fusion/]VmWare Fusion is probably the best option. The plus with Crossover is that you don't need a Windows license for it, but both costs money.
If you have an old unused Windows license and don't want to spend further money it's either Bootcamp or VirtualBox by Sun, which both are free. VB is a less-featured emulator like Parallels or Fusion.
As for DOS games, forget about DOSBox, use Boxer. It makes DOSBox look as primitive as the games it tries to run. A real Gem. It's quick and easy in the natural Mac way.
Really, you'll never look back.
The beauty with Boxer is that it packages your games once they are installed into typical OSX applications. Meaning, GoG could quite easily sell ready to install DMGs (sort of setup files for Mac if some PC user wonders) for Boxer use. Just drag and drop and run, no setup needed. (well, it would need Boxer installed, but it's a install and forget sort of app)

Is there anywhere on this site we can add "mac support" on a wishlist? It doesn't really fit in the add-this-game wishlist.
The old DOS games shouldn't be too hard to ship with DOS-box/boxer/whatever, and some newer games have (admittedly, hard-to-find) mac versions. Whether those versions are native (Blizzard's games, Neverwinter Nights, and any other made before the switch to Intel), or emulated like many recent games (Spore comes to mind) isn't really a big deal - I'd like to see that those games that can be packed for the mac (without porting or needing to install another application separately, of course - everything neat and tidy in a single .app preferably) are made available to that platform (but then another can of worms is opened - what about linux and other systems?)