For clarification, I'm not asking about getting the games to simply work on modern hardware/software.
A lot of old DOS games had low max resolutions. Many (like Jagged Alliance: Deadly Games) maxed out at 640x480. Modern monitors have such high PPI (pixels per inch) that playing at the native resolution puts the game into a tiny letterbox. Playing fullscreen stretches the textures out causing a pixelated mess.
Is there a good way to display these games at a good size without just getting a monitor with a lower PPI? I suspect there's no good solution but maybe something exists that's better than what I do, which is just play in a tiny window.