Note: This summary excludes the following games because you already own them:
. Fallout 3 (Yes it IS an RPG)
. Mass Effect
. Lost Odyssey
. Eternal Sonata
The following are in alphabetical order with my top 5 in order at the bottom, this is so you don't judge the games information by my personal views.
Blue Dragon
A turn-based JRPG, in the same style as Lost Odyssey (it was also designed by Mistwalker studios). It has a "cartooney" feel to it, as it's aimed towards a slightly younger audience, however the gameplay is excellent with a battle-system possibly better than Lost Odyssey's.
Characters are ok - nothing special, but the art design is excellent with character designs by the guy who did DragonBallZ. Music is steller and it spans 3 disks.
There is a demo, to test the graphics, combat etc... but its doesn't represent the game very well.
Fable II
A WRPG by Lionhead studios I'm a big fan of the Fable games. The story is terrible, but the world is engaging - as you can take up jobs, interact with civilians and see your actions and moral choices effect the world directly.
Combat is action-based, it's real time and consists of Magic, range and melee. It's fun and works well, although the game doesn't take much skill to beat.
The art is excellent as is the music, but the gameplay is rarely immersive and the story is terrible. It has online Co-Op and you can try the opening section on XBL.
Infinite Undiscovery
An action JRPG, it has a great story, with interesting characters. The story is really very good in this game, despite holding may clichés of the genre. Graphics however are not. The art design is nice but it looks like a PS2 game in most places.
Combat is real time, with a large number of combo's and items to use. It uses a party system in which you and 3 A.I partners fight at once in real-time.
It's a bit short but spans 2 disks.
Oblivion
Not much to say since you've played Fallout 3 - it's that in a fantasy setting...
Sacred 2
A very large game in scope, a poor story and graphics are missed due to the fun co-op (it's best to play with friends on this game) and combat system.
It'll take a very long time to beat and plays a lot like Diablo, with a class based character system.
If you ever buy this I will play Co-op =p.
Star Ocean : The Last Hope
A game by Tri-ace, the guys who made Infinite Undiscovery ^. They are very similar, except Star Ocean is set in a space setting and uses a arena-based combat system that is boring. It also has a shit story, with seriously annoying characters although the settings and events are interesting.
It spans 3 disks.
Tales of Vesperia
An anime looking game with an action-based combat system. The combat is arena based with 4 characters but unlike SO : TLH combat is deep and fun.
The story is great, with a large world and a number of events. Characters are interesting, and skits (little comic book style scenes) help flesh them out.
The game is very long, despite being on a single disk, and will take at the very least 40 hours.
There is a demo, but it doesn't represent the game well, use it to see if you like the art style and the combat system (that is dumbed down for the demo).
The Last Remnant
A Square-Enix game, it uses the Unreal engine to produce stunning graphics, but there is a lot of lag and the graphics load in late - however the effect is quickly ignored.
The story is good, with some interesting characters, and it will take a while to beat. If you want to beat all side-quests it'll take over 100 hours over 2 disks.
The game uses an innovative turn-based combat system that is for the "hardcore", you have to learn how it works to succeed. It's fun to use, although the game almost plays itself at times.
Too Human
Got a lot of stick due to hype, but it's not a bad game. The real-time combat is tough at first although quickly becomes addictive. A poor story is saved by great cut-scenes, although the repetitive enemies and environments (really repetitive) can get stale fast.
There is online co-op and hoarding for items is fun and rewarding.
My order----------------------
Ok - my personal top 5 out of this list in order:
1. Tales of Vesperia
2. Infinite Undiscovery
3. Fable II
4. The Last Remnant
5. Blue Dragon
Note: There are 3 games out the 4 not listed that would have made it on that list had you not already owned them.
Although the best for Co-Op is easily Sacred 2.