A lot of people have said "rides for seniors don't have to be boring, enough with the sitting on the bench stuff!" And I agree with this, however here are the criteria that I use for thinking about what's good for a senior, add any you guys can think of:
1.) Capacity for a longer attention span.
2.) More interested in history/nostalgia.
3.) Less banging you up. Not as much of a concern in Disney as in some other parks.
What else?
Yeah I think sharing information becomes more vital than thrills as you get older. I would have thought "Oh Canada" was pretty boring as a kid, but I enjoy it as an adult. Kids are all about flashing lights and bangs!
Capacity for a longer attention span is great once inside the attraction, but I think that shorter and/or more comfortable queues are a draw as well. I don't know many seniors that are content standing in long queues with nothing to do, especially if they're traveling with antsy grand children.