With the releases of the God of War and Sly Cooper collections out, and the Shadow of Colossus/Ico and Tomb Raider collections on the way, it's apparent to game developers that this sort of thing is a good idea. While these compilations haven't made nearly as much as other games, these games cost much less to produce. All they really require is a new coat of paint, and maybe a little debugging. That being said, there are a lot of last generation classics and this would help them get around that whole backwards compatibility thing. These are just some of the series that might be worth putting into a collection.
The Digital Devil Saga Collection
Atlus' Digital Devil Saga was a great RPG at the time. With a great battle system and some great graphics for its time, this Shin Megami Tensei game easily rocked the boat back in the PS2 days. Besides that it also became quite difficult to find if you were late to the party. Both games alone would have cost you at least $100 before Atlus rereleased it a bit back. It's about time Atlus gave PS3 owners a great Shin Megami Tensei title for a good price. Just remember to get an extra copy for Ebay.
Devil May Cry Collection
Say what you will about Devil May Cry 2, but the series is easily responsible for making action games what they are today. Killing with style didn't start with Bulletstorm, and it could be said that without Devil May Cry that concept might never have ever been developed. Besides that with the new remake of Devil May Cry in development, it might be a good time to capitalize on the series' rebirth and introduce a new batch of people to the white-haired demon slayer.
Metal Gear Solid (Subsistence) Collection
Snake's quest is over, but it's not hard to say that Metal Gear Solid was one of the games that made PlayStation what it is today. That being said, Snake could sneak back in the form of a compilation box, with the Subsistence version of the games being on blu-ray because who doesn't want to see Snake skateboarding in HD? While we're at it, we should probably bring up Twin Snakes. While the fan favorite is the original PlayStation classic, it should be obvious to most that it is horribly out-dated. While the Game Cube remake is much easier, the graphics update would help get more on board for the game. That and not playing with old school Resident Evil controls. A push to include the port to a Sony system definitely would be a big bonus.
Final Fantasy Collection (1-10 and 12)
Out of all of these this is the most unlikely. While Final Fantasy does have a nice fan base, it is doubtful that Square-Enix would spend the time on it. Even though most of the early games have in some way been on a PlayStation system (the exception being Final Fantasy III) Square-Enix probably wouldn't do it. In fact they won't remake Final Fantasy VII because they feel they'd rather put more money into future products (like remaking Dragon Quest V).
These are just some of the many games that deserve HD remakes/collections. Will they get them? Well, that's up to you to decide. The better these collection games sell the more they will make. Keep an eye out for the many collections coming in the next few months, and show Sony we want this! Also don't forget to comment below on what games you think need HD remakes or collections for the PS3!