Here is some information readily available, but rarely organized in an an easily visualizable fashion. Here is a distribution of gross terrestial relief features, percent of the earth’s surface as a function of elevation. ( Source: “Physical Geography”, Strahler, 1975).

Elevation (Km) vs % of Earth’s Surface

Continents (29%)
5+, 0.1
4 to 5, 0.4
3 to 4, 1.1
2 to 3, 2.2
1 to 2, 4.5
0 to 1, 20.8

–Sea Level–

Oceans (71%)
0 to -1, 8.5
-1 to -2, 3.0
-2 to -3, 4.8
-3 to -4, 13.9
-4 to -5, 23.3
-5 to -6, 16.4
-6 or more, 1.0

This material is represented graphically in Strahler and it gives you a good intuitive grasp of the overall geomorphology of the planet that no table of numbers can give you. A vertical resolution of one km is pretty coarse, it would be interesting to run some hi-res global digital terrain data through a GIS system and prepare a table like this at a finer vertical sampling interval, and then assign those categories to colors for a thematic map.