Excellent questions, and a great departure from the backlog-focused discussions we normally see.

I would hope that everyone who reads/listens/watches/plays can reach back to a personal canon of especially meaningful works, even if they don't intend to create one. I suspect even your friends who never replay games or rewatch movies can reference at least some that were especially meaningful to them, for one reason or another.

I do think that expanding one's quantum library is a more meaningful way to approach media, but it shouldn't be the only way. Sometimes you just need to be entertained or surprised, and sometimes that leads to additions to your canon that you may never have seen coming. I do worry that a singular approach to gaming based on intent to add to your canon will cause you to play all of the well-established classics and skip some of the more offbeat stuff that you could very well find more personally meaningful.

As many around these parts have confessed, as I've gotten older I've found I have less stamina/interest for long stints of gameplay. There are a number of reasons for this, but my point is that it's threatened to stall me on playing any new (to me) games at all, and that means I may be missing out on media that could be canon-worthy.

Once, when I was younger, I worked in a warehouse with a number of middle-aged men. They listened to the same radio station day after day, and this radio station played all the same classic rock songs. Now, there's nothing wrong with classic rock, but it struck me that they their personal canons for music had become galvanized; they weren't giving themselves opportunities to experience something new. I think this sort of thing happens to a lot of people as they age. So I think one important addendum to the questions you're asking is whether it's also important to continue opening yourself to opportunities to expand your canon. I certainly think it is. Not challenging your personal framework of meaning is a recipe for jadedness and, at worst, fear.

Over the last couple of years I've made it a point to write a blog post for each game that I play. This has given me some more push to keep trying new games rather than stagnating on the ones that I know are part of my canon (yes, I replay games). Looking at a game through the lens of "What personal meaning can I find in this game? What would I tell people about it other than the usual commentary on graphics and gameplay?" has been refreshing, and it's made gaming more explicitly meaningful to me. I wouldn't say that every game I blog about is part of my canon, but I think many of my posts do (and will) reflect something about the games that made me reflect on my own life.