On a screen as small as 40" (which will do me for a while) there's an obvious improvement in picture quality between BluRay and DVD -- when the effin' BluRay disk will play on the player. The BluRay "standard" is a bucket of vipers.
The problem is, BluRay was inferior to HD-DVD, but BluRay won the format war because of decisions made at a couple of studios.
The coming problem is, 4K TV is starting to arrive, and by the time we're shopping for Christmas 2019, 4K TVs (which are obviously going to be very large screens, otherwise the eye isn't impressed) are going to be below $500-$600 and 8K TV is breathing down everyone's necks. Digital distribution of new release movies to theaters hasn't caught on, which is difficult to understand. Probably has something to do with the Mob activity that governs so much of the entertainment industry machinery.
Optical formats will remain available, of course, probably for some years (the last VHS maker stopped making recording decks a mere two years ago; players are still available, not sure whether they're being made), but solid state digital (both streamed and on media) are going to, quite simply, destroy the market for optical media. A visit to Walmart, with its bins of movies and CDs under $10 (mostly $5 and under) should convince most people.
I can probably do without 4k TV and live through it. lol They do have HD Media Players that will hook to anything even old RCA red/white/yellow inputs that stream, play SD cards, and USB sticks.
But you know what the problem with all this mess is? The fact that it is illegal to copy anything, even just for your own use. This should be legal so you can copy all your old stuff onto SD or USB for your own personal use. This way all the VHS, DVD, Blueray stuff you have already invested in can be reused.