I know I'm fitter at 55 than my mother was, but I don't know how much of that is down to what exercise I do.
I've been doing karate for 21 years. Used to train 4 x a week, now only once or sometimes twice. A lot of those in my class are in our 50s, having trained together all that time, so we're all very aware of our limitations and what we can do to mitigate them. For instance, karate can be very hard on the knees, so we take care to do more thigh-strengthening exercises. We keep working on flexibility too- although it can go very quickly if you have a couple of weeks off!
To continue thigh-strengthening and add in cardio, I cycle a lot with ds2. I also do long walks as and when I can fit them in (decent pace, not an amble).
Then other physical challenges such as a mountain climb, or building an extension!
I do know that I was shocked recently when my friend, who is the same age, told me that she can no longer put on her pants standing up. Obviously balance is fairly key in karate so I have no issues putting on knickers standing up, but it did make me wonder what the general standard is for my age group.
I think a rounded mix of exercises is probably our best bet- lifting weights is great, but you probably should have some flexibility stuff and cardio in there too.