Jester David
Hero
Or Pathfinder. Or 13th Age. Or Shadow of the Demonlord. Or the World of Warcraft RPG.But that ignores the spells, the monsters, and the race and classes. Those, more than anything else, give D&D the closest thing it has to a set identity.
You can make any sort of lore changes you want, but if you can play an elf wizard casting fireball at a goblin with 6 HP and a 10 Dex who rolls a d20 to save, it's pretty much D&D.
(But not, ironically, 4th Edition D&D as the wizard would make an attack roll instead of the goblin making a save...)