When I think about dwarven fortresses, I think about steep cliffs and gorges; helms deep like valleys with a single access side to defend; towering mountains with small paths and passes; huge cliff faces in which the entrance is dug; soaring rivers in spring that carry everyhing in their course, etc etc
In DF, you have gentle slopes, little hillocks, and gentle streams, sometimes smaller, sometimes larger, but never threatening. Every hillside can be walked on and there are no natural defenses save what you hack away yourself. In a sense, we should call it hobbit village rather than dwarf fortress.
As far as I know, the only impressive terrain features in DF come from streams meeting, and very seldom a lone stream in a canyon.
IMHO, dwarf fortress terrain needs to be made less gentle, especially the more mountainous parts:
1) a lot less slopes should have ramps, and there should be more sheer drops. If you look at a real mountain, you will see that most mountains are accessible along some sides, but have cliffs on other sides. An example is Scotland's Ben Nevis, which as a mountain is nowhere near to being extreme; it has a relatively gentle south and east face but in the north has mainly cliffs that are inaccessible except to dedicated mountaineers, and certainly not to an army wearing full plate armour. On a smaller scale, even the accessible sides have a lot of parts that are unpathable and you need to walk in between the steep parts.
2) terrain should have consequences, both for hauling and for military. Moving heavy stuff should cost much more time/energy along slopes, both upwards and to a lesser extent downwards. Armour should have greater impact on movement along slopes and staircases. Fighting from higher ground should give advantages. Presumably, dwarfs should be hindered less by the terrain penalties than elves/humans/goblins, as they are supposed to be mountain creatures, after all.
3) climate should be more altitude dependent. A mountain should be snow capped in many climates, and winters in the mountains should feature a lot of snow and even passes that become inaccessible. Dwarfs out in the cold on a mountain top in mid-winter should become unhappy if not frost-bitten. Streams already freeze in winter in some climates, but they should flood over in spring, and in some climates there should be seasonal streams. There should also be more variation in streams, not just either flat or huge waterfall, but also streams that run down a mountain side or in between mountains, losing altitude as they go.
Anyway, I know the list of desiderata for DF is large, but this is something that has been annoying me....