Quake ran smooth on a Pentium 100. Half-Life absolutely wouldn't have, even at 320x240.
Like I remember Doom running fine on my 486 SX 25Mhz, but looking back at it now, it wasn't that great. It took a top end Pentium to really get it into smooth-ish 20fps+ territory.
DOOM wasn't fine on Am486DX4 100MHz and Ziggurat Vertigo was like 5fps at best on it.
Are you happy now?