One that does have stairs is Splash Mountain. Another is the WDW Railroad at the Main St staion and the Frontierland station.
Most of the queues don't have stairs so that the queue will be accessible to wheelchairs and
ecvs.
Some do have ramps, but most of the ramps are fairly shallow.
Here are some with ramps:
Pirates has a moving walkway ramp to get out of the unloading area. (It also has an elevator).
Small World has a very shallow ramp.
Tomorrowland Transit Authority has a moving walkway ramp to get up and down from the second floor loading area.
Test Track has a long ramp in the queue.
Spaceship Earth has a ramp to get into the building, but there is an alternate place to board at the exit for people with ecvs/ wheelchairs.
The Land has a long, fairly steep ramp to get into the building and a ramp inside the building to get down to the level where elevators are located.
The Backstage walking tour at the Studio has a ramped area in the beginning of the queue.
if you ride the monorail, the monorail station at MK and at the TTC have long, steep ramps, without a way to get around them. Epcot does also, but there is an elevator.