All aircraft designers try to make the a/c as light as possible. In the case of the undercarriage assembly that means make the legs as short as possible, among other considerations. All the heavies you mention are low-wing with wing-mounted engines, so the length of the u/c legs has to be just long enough to ensure the engines are off the ground at all times (including a bit of wing flex at touchdown) and the rear fuselage doesn't hit the ground at normal rotation on departure.
But this does not seem to work on 747SP...
747SP has exact same wingspan and wing as -100. The engine sizes should be same. The fuselage is shorter, so the rotation should be less limiting.
Why does 747SP stand taller?
As for roof heights...
On 747 classic, the minimum roof height is 970 cm.
On DC-10, the nominal roof height is 825 cm.
On empty A310, the roof height is 755 cm.
On 767-200, the minimum roof height is 719 cm.
On empty A330-300, the roofline slopes between 774 and 853 cm (and more...)
On B777-200, the roof is between 839 and 868 cm as mentioned.
On loaded A380, the roof height is 1080 to 1081 cm.
On 747 classic, the roof is about 213 cm above upper deck sill. Observe that this leaves quite limited headroom on upper deck.
On DC-10, the distance from maindeck doorsill to roof is 345 cm.
On A310, the distance is 301 cm.
On 767-200, the distance is 305 cm.
On A330-300, the front doors are 300 cm below roof, and rear door is 279 cm below.
On B777-200, the distance from doorsill to roof is about 368 cm.
On A380, the roof is 292 cm above upper deck sills.