Doom is the standard first test on every DOS machine I put together — see the OptiPlex 380 retro build, where it was, unsurprisingly, the first thing tried and it worked beautifully. It’s the reliable benchmark too: software rendering performance in Doom is one of the numbers I actually track across different retro PCs.
It’s also a good general-MIDI test case alongside mt32-pi and the Dreamblaster X2/X2GS — the soundtrack holds up well across FM synth, MT-32, and General MIDI playback.
And it’s been ported and modded in every direction imaginable, from software-rendered voxel remakes (Voxel Doom) to Commander Keen-style WebAssembly browser ports of other id Software-era classics.