The last 3 id tech engines seem more like tech demos than well-rounded general purpose engines. id Tech 3 : curved surfaces id Tech 4 : unified lighting id Tech 5 : Virtual Texturing (MegaTexture)
Rage has virtually no physics in it. I punch a skull attached to a rope and it makes a "thwump" sound and produces a small cloud of dust, but stays stationary. Even traffic cones won't budge. There's no HDR, which can be quite important for games with mixed indoors and outdoors.