Remastering older and retro titles for the newer consoles has been a trend the last few years, seeing Darksiders, Dark Souls, Dark Souls II: Scholar of the First Sin, Crash Bandiccot: N'Sanity, and most recently, Shadow of the Colossus for the next-gen consoles (Xbox One, PS4). I very much appreciate these remasters as they allow me to play updated and polished versions of games I love (my original Shadow of the Colossus does not want to run smoothly on my PS2 anymore), I do have to wonder what stops companies from doing this justice to more games.
Granted, the answer is pretty obvious, numbers and fame, most of the time. Remastering Darksiders and Dark Souls were no-brainers, as those are consistent titles which were well received. Dark Souls II is a fantastic game as well, though a bit underrated compared to the OG. Crash and Shadow of the Colossus I assume were mostly nostalgia driven but certainly made huge splashes in their time. I suppose this is more my way of trying to justify why some of my favorite games have yet to be remastered.
Some reasons for a lack of remasters is that they can still be accessed through other portals or services, Persona and Persona 2: Eternal Punishment can be accessed through the PlayStation Store for the Vita and PSP. One could argue that Persona 4: Golden for the Vita was the remaster for Persona 4 (easily one of my favorite games of all time), though I am surprised that Persona 3 has not received one.
Maybe after the hype for Persona 5 Atlus will decide to grace us. Most recently I came across a discussion where some folks were clamoring for a remaster of Ni no Kuni: Wrath of the White Witch. Quickly these musings were shut down by putting down the game or suggestions of simply getting a used PS3 and enjoying the game that way.
Indeed, the criteria for remastering seems fickle at times. The Metal Gear Solid titles were finally remastered from PS2 to the Xbox 360. but left there. Other reasons are, of course, the technological challenge of upgrading certain games to certain systems, as well as the popularity. Perhaps the success of Phantom Pain did not really inspire too much of a resurgence for MGS fans to get everything remastered for next gen. Dark Souls has certainly earned that right, there's just no stopping the Soulsborne train.
These games and titles mentioned here are of course only ones that I play or am interested in and by no means a full measure of the great games that have been remastered or left in their era.
That said, there are plenty of games that I would very much like to see remastered, that I might enjoy without needing to go out and purchase a used console for only a game or two (that said, I got my PS4 exclusively to play Bloodborne and persona 5). Darkstalkers and Puppeteer are some titles that I would definitely like to see brought to newer consoles, should it be feasible.