My husband died 15 months ago, aged 68, so this thread has prompted a few thoughts:
A cousin, also a widow, sent me that quote in full, "I have plenty of people to do things with, but no one to do nothing with." It's one that makes many widowed people go "Yes, yes!". So true.
As for what to say - well, almost anything is better than nothing. For me, the most helpful things were kind and fond recollections of my husband, and gentle enquiries about how I was feeling. I think the comments such as "a good innings", or "at least it was quick" (if it was) etc should be left to the bereaved person -they can introduce these postive thoughts, but it can be hurtful if others do so when the bereaved person is just needing to express their pain. Don't try to minimise their loss.
I have really appreciated it when friends who are still couples have continued to include me in events and activities, inviting me out for a drink, a meal, a walk, etc. Having someone to go shopping with can be helpful in the early days, when crowded places can freak you out.
And if someone loses a spouse, DON'T compare it to when you lost a parent or even a sibling, and certainly not to the death of a dog or cat! Most people who are widowed will already have lost one or both parents, and the loss of a husband or wife really is something quite different, much more intense, and not the same at all.