I was fortunate enough to know both of my maternal great-grandparents pretty well (even better than my grandparents, I'd say). They were both wonderful, wonderful people - always so full of life and love, and I'm so blessed that I got to know them.
My great-grandmother had suffered a stroke and congestive heart failure, but even though her body was weakened, her spirit was strong as ever, and she would always insist on cooking delicious meals for us whenever we came to visit. She made sure the candy jar was always full for us kids, and was just a wonderful, sweet, strong lady. She was smart, too, and one of the most optimistic, positive people I have ever known. "There's something good about everything" was her signature phrase, and I still try to remember her wisdom when things get tough in my own life.
My great-grandfather (we always called him Papa, although to this day I'm not entirely sure why) was a fit and strong yet gentle man - he was always willing to take me and my brother and cousins on tractor rides, or show us some new trail he'd found, or teach us how to do all sorts of neat things around the farm. He was usually pretty quiet and laid-back around the house (although he was very active and a hard worker on the farm), but he could be wickedly funny, too, and he used to tell us stories and jokes that would make our sides hurt from laughter. The two of them together just seemed to radiate love and contentment, and for me they always seemed like the perfect couple. They got married young - I think he was 18 and she was 16 - and they stayed together for the next 70 years. I never once even heard of them fighting or arguing about anything (although I'm sure they did occasionally - they were human, after all).
Papa died when I was about 14 or 15, after a tractor accident that left him pretty much incapacitated - paralyzed from the waist down, if I remember correctly. They put him in a nursing home, which he hated, and he slowly lost the will to live. I miss him greatly, and I feel like if that tractor hadn't overturned, he would've had several more good years of life...but part of me's kind of glad he didn't live to see his 90th birthday. Why? Because that would've been on September 11, 2001, and I think that would have hurt him greatly to live through that...so part of me is glad he found peace before then.
Great-Grandmother passed away a year or so after Papa. She had been in ill health for many years, and at that point had outlived not only her husband, but all of her children as well. I was sad when she died, and I still miss her. She was a wonderful woman, and Papa was a wonderful man. I guess the good thing is that if there is a Heaven, they're together again...and just as much in love as ever.

Peace.
(Wow, that was a long piece! Sorry about that...I tend to ramble when I get thinking about things, especially those close to my heart - and both of my great-grandparents certainly were.)