Great thread, and that's a pretty good list, too.
Here's mine, and like you, when I really think about it I'm a little surprised at some of my choices:
Zeroigar -what can I say, I'm a shooter fiend at heart
Zenki FX -great replay value, this action platformer never gets old
Chip Can Kick -see geepee16's comments
Nirgends -this game is constantly hyped and yet I've never really ever sat down with it
Dragon Knight IV -see Nirgends
Detective Ladies -this games just looks awesome, plain and simple
Yuna FX -because of the fact that I've cleared Yuna FX, there are a ton of really fun minigames I've unlocked that have great pick up 'n play value. after you've cleared Yuna, the disc basically becomes a 10-in-1 disc full of minigames: Doki Doki Slots, Memory, even a sidescrolling shooter-esque (no shooting involved, though) space game where you fly around and collect objects, etc... fun!
Battle Heat -out of all the "easily accessible" FX games I own, I've spent the least amount of time with BH. I need to give it the attention it deserves and learn the nuances of it's one-of-a-kind game engine
Der Langrisser FX -scenario 13 has been consistently kicking my ass. anyone know how many scenarios there actually are? every time I think I've reached the end they throw another scenario at me.
My list sticks strictly to the games that I already own.
Last Imperial Prince is a great game George, I cleared it last year. Definitely one of the system's better games, some of the locations look extremely nice later in the journey. The final area that takes place on a snowy tundra & ice caves is one of my favorites. Also, the desert area. My only insignificant gripe is the strange battle system. You never know how many enemies you are fighting at any given time and while some battles are over quickly, some battles seem to rage on for 15 minutes or more. The actual battle mechanics are really good, but some of the exchanges could've been shortened considerably.
Is Power League FX any good? I've been trying to get that game for ages, and yet it is NEVER on eBay. I saw a copy on eBay the other day for the first time but it was like $60 after shipping which seems waaaaaaaay too high to me.
Same goes for Shanghai: The Great Wall (I'm a sucker for Shanghai games, what can I say), which I've actually never, ever seen on eBay. I'm beginning to question it's physical existence.