The original DOS version of Doom runs at 35fps, exactly half of the 70Hz refresh rate of 320x200 VGA mode. I thought it felt really smooth back in the day, but it does feel weird and stuttery on modern systems when played through Dosbox. I get used to it after a bit, but still.

Fortunately as Doom is open source, there are many enhanced Doom ports that lift this 35fps limit and allow it to run on modern machines without emulation. I usually play in GZDoom which can run at the max refresh rate of my monitor (144Hz), so it feels silky smooth.