Actually, Nintendo published games are usually compatible with both hands, but 3rd party developers just ignore lefties. Even such a large developer like EA "forgot" to include a left handed option in EA Sports Active. It was one of the best selling games and it got significant criticism from lefties. In the next game EA Sports Active More Workouts, this issue was corrected and a left-handed option was added, however it was a just a small tweak and the game still felt awkward while playing with my left hand. In Wii Sports, I never feel awkward because of my left hand usage, though. Blame 3rd party developers who just focus on game development, not the user experience.

Team Fortress 2 is a nice example. They offer new content and updates totally for free. (They indicate that the game cache size double over two years with additional content.) Although it's been released long ago, people still purchase the game because it's kept alive with these updates. And since the updates are free for current users, they do keep their current customers satisfied. Instead of making the current users pay for additional content, they prefer to increase their customer base. I wish all game developers adopt a similar model.

The games you are asking work well in Windows 98 so you can install Windows 98 on Dosbox just like any other dos application and then install Starcraft, Diablo, etc. on this "virtual Windows" and let Dosbox do the scaling for you. For Dosbox, it's just only another app so I don't expect any problems with the scaling. I am not sure about the performance but it's worth a try. (You can also try this with windows 95 for better performance.)