As a baby-boomer, the first TV generation, I've been watching movies on the tube since the 50's. Of course, it's a different experience than going to the theater, not necessarily better or worse, but certainly different. It might be better to fully appreciate a great film in the isolation of a darkened theater, but a mediocre movie is easier tolerated at home.
Television introduced me to some classic movies that I eventually saw on the big screen; Citizen Kane, the original King Kong, and Blade Runner come to mind. The accessibility of TV has also enabled me to repeatedly enjoy what I consider great scenes in less than great movies. A recent example is Meryl Streep's "hire the smart, fat girl" speech in The Devil Wears Prada, but there are many others. There are also movies that I think of as having seen many times but eventually realize that I've never seen the actual beginning until I happen to catch the whole thing.
Then there is the topic of buying favorite movies on DVD, VHS, or whatever is the popular format of the time. The Big Lebowski, and National Lampoon Christmas Vacation were thoughtful gifts from our children, but they've been watched many fewer times than when they've shown up on the channel rotation. It's possible that we've never watched The Godfather Trilogy in a box DVD set which was a Christmas gift six or seven years ago, but Pam and I will watch at least the first two anytime we spot on the TV listing and we're available.
We are not alone in this behavior, apparently. Not long ago, I heard Steve Van Zandt discussing his sometime occupation of disc jockey (along with musician and actor) on his satellite radio channel. He rhetorically posed the question of why middle-age people who owned a huge amount of rock music on record, tapes, and CD's still listened to disc jockeys on the radio. "The same reason you seldom watch movies you own, " he said, answering his own question. "It's the element of surprise of hearing the song or seeing the movie at a random time when a disc jockey or TV station chooses them."
That's the best explanation I've heard.