As educated gamers many of us have played excellent titles that somehow got lost in the main stream shuffle and damn it I want them back.

Here is my list of games most in need of a sequel

1. Psychonauts- This is probably Tim Shaffer's finest game, yet it sold under 500,000 copies on PS2 and Xbox. I want a sequel to this amazing platformer right now. Gamestats score  88 on Xbox, 87 on PS2

2. Beyond Good and Evil- Ubisoft has been supposedly working on the sequel to this amazing Zelda clone (only similarities I found were in the combat) Gamestats score 87 on PS2 and GC, 90 on XBOX

3. Eternal Darkness Sanity's Requiem- This is IMO the best game on the Gamecube, and one of the few games genuinely scary. If you thought Dead Space was good an HD remake or Sequel to this game would blow Dead Space Away. Gamestats Score 90

4. Tomba- this series was a platforming gem on the PSone with Gamestats score  of 90 for the first game and 86 for the second it is deserving of a reboot. This game is also the second game on the list staring a pig.

5. Odin Sphere/ Grimgrimore- this beautiful 2d rpg was launched late in the PS2's life and like most Atlus games has yet to find a big audience despite being amazing. Gamestats score 83.

6. Skies of Arcadia- This is and was one of the best reasons to own a Dreamcast. Amazing story, great ship battles and even though it was re released for GameCube it still hasn't found the success it deserves. Gamestats score 9.0 Dreamcast, 8.6 Gamecube

7. Vagrant Story- The RPG theme continues as we look at Square's Epic PSone game. The ability to target individual body parts made this one of the most unique and critically acclaimed RPG's in the era. Gamestats score 9.2 

8. ICO- this game combined with Shadow of Colossus are at the core of games as art and for good reason as the story visuals and music are remain beautiful to this day. Here is hoping we do get the HD remake. Gamestats score 9.1

9. MDK 2- The dreamcast version was one of the hardest games ever but that didn't stop the much easier PS2 version from being a great game as well with great action and huge boss battles. For all you skeptics it was made by Bioware. Gamestats score 8.7 Dreamcast, 8.0 PS2

10. GunValkyrie- This XBox game is the epitome of challenging. The game play is fast and intense. Consider a remake to this game to be Super Sin and Punishment because it is that much more intense. Gamestats score 7.7 (haters)

There are many many more games so sound off lets see your hidden gems. 

First off, not every game needs a sequel.  Some games can stand fine on their own.

Second off, Odin Sphere is an awful game.

The most hidden of my gems is probably I-Ninja. It was a last gen game and a very cool one.

Watch that TV ad.

I Ninja was pretty awesome. 

Little King's Story is one of this gen's best hidden gems

Jam with the Band is worth a mention as well

demon souls IMO is a hidden gem its just an excellent game

Anyone remember when Disney games were good. Aladdin, Chip and Dale, Darkwing duck, Castle of Illusion etc. If they weren't hidden gems when they launched they are now after such a bevy of crappy kids games lately. 

The Guardian Legend

Battleclash / Metal Combat

Timesplitters

all of these NEED sequels

Breakdown on the Xbox.

And IMO, MDK1 >>>>>>>>>>>>>>>> MDK2.

Depending on what qualifies as a hidden Gem.

Is it low sales and how low?
In which case I'd say
The World Ends With You
Demon Soul's
Valkyria Chronicles
Beyond Good and Evil
And maybe Wipeout HD (how were the sales on that?)
Jet Set Radio Future: Though they did bundle it with xbox

I'd give all those a 9/10 except for TWEWY I'd give a 9.5

Is it a game that I think is good but got a meta under 80... well that's Smaller

Dreamfall: The Longest Journey rated a 73 and 75 on xbox and pc. I'd give that a 9
And probably Episode I, Podracer I'd give a 9. Don't know what it's rated