I've completed QFG 1-4 with a Magic User/Wizard. 1-3 ran pretty well, no real issues, as long as you can stomach 320x200 resolution 256 color graphics. QFG4 had a bunch of issues. I had to download some patches for the game, and I ended up having to tweak my DosBox settings to get the game to work properly. But once I got that setup, I was able to complete the game.
QFG5, though was a different story. This game, created in 1998, is a Windows game, not DOS, so I can't use DosBox as an emulator. All sorts of graphical glitches. I had to install a patch just to get it to run on a 64-bit OS, and even then it ran very badly. I ended up getting a Win98 virtual machine image and installing that. There are still some weird graphical glitches, but it's playable, at least.
QFG patches:
http://www.sierrahelp.com/Patches-Updat ... dates.html