I would like opinions of people who have had a truly hard time getting particular games to run. I mean they should have had a hard time running them under DOS, not Windows 3.1, 95, 98, NT, 2000 or XP. These games should be difficult to get to the main menu, nevermind getting the game to run smoothly or with the best graphics or sounds.

Ultima VII and its sequel Serpent Isle are not truly difficult games to get running in DOS. It may be difficult to get them running with all the bells and whistles, but all you need to get them running is a 386 or better, 560KB of free RAM and 2MB of Extended Memory. Most people have trouble if they have expanded memory even mentioned in their config.sys, but eliminating any references to it will go a long way to get the game to run.

Many DOS games choke on non-Intel processors, graphics cards that are not 100% VGA compliant, Sound Blaster "compatible" cards, or non-Microsoft versions of DOS. Some older games will refuse to run on too fast computers (Ultima II will likely give a divide by zero on a 486) or with too much RAM (California Games's RAM checker wasn't built for RAM above the 1MB barrier.) Buggy or unusual drivers will stop many a program in its tracks.

I can imagine that truly performance-busting games (think flight simulators) are very, very picky about the hardware they will work with. I would imagine though that Super VGA games will give the most headaches because they rely on individual cards and drivers more than universally applicable hardware programming methods. No standards here.

It could be that a program was poorly programmed or tested on only a few or similar systems.