I recently found a source port of
Diablo 1 called "
Devilution X." It's a faithful source port of the game with some notable quality of life enhancements.
For starters, you can bump the resolution to something far larger. Originally, the game was locked to 480p, so opening a menu window took up half the screen, and opening two of them on both sides blocked your whole view of the game. Not so with this port. Now you can switch around your inventory, view your stats, and still have a good look of what's around you.

You may notice a couple of other minor changes in this screenshot. Firstly, you can now use the Auto Map in Town, where-as before pressing Tab merely produced a message that the Auto Map couldn't be used in Town. Second is the fact that Magic and Unique items now have a different colored background, with blue for Magic and Yellow for Unique.

Another minor but welcome change is the fact that Pepin automatically heals you just for talking to him, rather than having to manually press an option to be restored to full health.

However, by far the best change this port makes is that it changes Gillian, an otherwise useless NPC in the original game, into a personal stash, just like the sequels. No more gold clogging your inventory. No more dumping your dragon's horde of treasure in the town square. Now you finally have a convenient place to dump your money and items into, with 100 pages of space for item storage. Shopping in town also counts your money in the stash in addition to your inventory.
There are tons of other changes as well, with plenty of options to pick from, but those are the biggest and most notable changes this port makes that I've seen thus far. If you haven't experienced this classic game, or want to revisit it, this is an excellent way to do so.