Right at the top of my list for franchises I want to return is The Legacy of Kain. Those games had an absolutely fantastic story, amazing voice acting for their time - although I believe one of the voice actors is now dead, so that could make things difficult, but Simon Templeman made an amazing Kain and I'd love to hear more from him - and were quite engaging, all things considered. Defiance was fairly satisfying, but the story could easily be carried on, and it'd be a shame for this series to just vanish.
Timesplitters is another series I want back - where's Timesplitters 4?! I'm not a huge fan of FPS, but these games were something special, especially the second one. At the very least, I'd like to see a HD collection make its way to the PS3 at some stage, maybe with some online multiplayer, because that's the one thing I remember about these games more than anything else: the multiplayer. This is pretty much all I played with my friends at one stage, and not many other FPS show the same ingenuity now that Timesplitters did back in the day (the Notre Dame level remains one of my favourite levels of all time, from any game) so it'd be nice to see this return.
I think we are long overdue a proper Banjo-Kazooie game, as well. Grunty's Revenge wasn't bad, but Nuts and Bolts was truly abysmal, and as a child Banjo-Kazooie was my favourite N64 game, and the second one was also brilliant. Even if this gets stuck on a Microsoft console only - which would annoy me no end - I'd like to see the bear and the bird make a glorious return.
Another Final Fantasy Tactics game, perhaps? Square Enix's recent performance - their refusal to localize Bravely Default and Type-0, the abundance of iOS games, and the general horror that is Fabula Nova Crystallis, which they're continuing with yet ANOTHER unnecessary sequel to the worst game they've ever made - has all conspired to make me lose a lot of faith in them...a return to Ivalice, to the complex political machinations and ambiguous moral situations, the delightful turn-based combat that, whilst not on the same level as Disgaea, is still enjoyable and complex, and the amazing soundtrack Ivalice games bring with them, would be more than sufficient to restore it. Ivalice has a rich history, there is PLENTY of room for another game in there somewhere.
We are long overdue another Valkyrie Profile game, too. Silmeria remains one of my favourite PS2 games, and I have been itching for a third chapter in the series focusing on my favourite Valkyrie, Hrist. Covenant of the Plume was absolutely atrocious; I think it's time for a PS3 version.
I also hope tri-Ace haven't forgotten about Star Ocean. I enjoyed The Last Hope - and I'm one of the few people I know that did - and I'd like to see something set between the second and third games, given the ridiculous time jump between them. Something MUST have happened in that time. But that aside, the Star Ocean series boasts unparalleled real-time combat (as good as the Tales series is, it still doesn't play quite as well in terms of 360 degree movement, which makes it a bit awkward at times) and quite often a wonderful story, even if it does like to load you down with awful complex terminology all at one point. Oh, plus nightmarish bonus dungeons, and a good character affinity system that lets you actually affect the ending a little.
Finally (at least for the moment) I'd like to see some more Ar Tonelico games...or at least something more satisfying than Ciel No Surge, which we will probably never see. I love the general feel of the games and, whilst the story isn't as good as it could be, the soundtrack is without peer, and it's nice to have vocal tracks that actually mean something in a game. Whilst a couple of characters in Qoga (Saki, specifically) got on my nerves, I also quite like the cast overall, as well. It'd be a shame for the series to die off after three games.
I think a return to the Heretic/HeXen games from Raven Software would be really nice, whether or not it's a Raven title. While a reboot would be okay, I think an actual Sequel would be better of course.
I loved The Tower of Druaga despite its extreme difficulty. There was something about the enemies, the characters, and the tower itself. Plus, I loved the official artwork for the series. For those who don't know, The Tower of Druaga is an arcade game from Namco released in 1984. It features a prince named Gilgamesh (usually called Gil for short) and his priestess girlfriend Ki. The game is kind of like The Legend of Zelda, but much harder, since you actually do need every helpful item to complete the game.
There were three more official Druaga games, as well as a roguelike released in 2004. The roguelike wasn't that great, but it has an impressive soundtrack that rivals any Final Fantasy soundtrack. (There is an anime, but sadly it doesn't use the same characters for the most part.)
Namco actually made a remake of the original for the PC Engine in 1992. This version is actually a lot more forgiving than the original. It features four difficulty modes (easy, medium, hard, and very hard). There aren't as many wizards (that was my problem - all the wizards) since the enemies are more diverse, you actually get to see Gil's HP, and the goddess Ishtar actually helps you in the easier modes. In the easy and medium modes there is no timer, so you don't have to worry about exiting. It's a shame this version is not available outside of Japan.
I wish Namco would market the Druaga series outside of Japan. Then more people would like them. And they haven't made a real Druaga game in a while. I'd like to see Gil and Ki again, and I'd love to hear them speak! (They do speak in Namco x Capcom, but sadly that's only in Japanese.) I was thinking of making my own flash game based on the Druaga series, but I don't have flash.
One interesting quirk is that Gil wears golden armor, and in Fate/stay night, there is a character named Gilgamesh who also wears golden armor. Maybe they got the idea from Druaga? (I'm not sure, though. The two Gilgameshes have very different personalities. Namco's Gilgamesh is a kind brown-haired guy, while Type Moon's Gilgamesh is an arrogant blond guy.)