I find all the rollercoasters at WDW tame compared to other parks, but here is my order:
Barnstormer, Seven Dwarves, Slinky, Space Mountain, Thunder Mountain, EE, RnR.
The only one that bothers me is RnR, only because I tend to get my neck hit on the sides of the restraints.
If instead you want to rank it in terms of fun (the last one is the most fun):
Barnstormer (uncomfortable for adults, lazy theming, too short, not very exciting)
Space Mountain (iconic, but too rickety, can't really see anything, doesn't have improvements that the version at
Disneyland has)
Seven Dwarves (points for the dark ride parts, the rest of it is rather boring)
Slinky (good family coaster fun)
RnR (uncomfortable, dark, but otherwise it's good times)
EE (drops, yeti, and going backward are all good times)
Thunder Mountain (pure fun)