You could do an entire thread of favorite Ryudo quotes. My favorite Ryudo quotes were "Princess, the powers of darkness aren't coming this way to tell us about the neighborhood bake sale. We have to get out of here NOW!" and "What's up with you and this 'cleansing' thing? Somehow I doubt your soldiers are carrying soap and bubble bath under their armor."
I'm generally not a big fan of the Grandia series (the battle engine in the Grandia games divine; everything else is mediocre at best) but II was easily IMO the best Grandia game and Ryudo did have some zingers. I'm with you Dice in the fact that Ryudo stopped being interesting when he stopped being a jackass and became a nice guy.
But my favorite quotes from games under RPGfan's coverage come not from RPGs, but from graphic adventures. One quote I found amusing in The Longest Journey and still find amusing is when you point to a book on April's desk and she says "I'm part of the should be reading more but [don't really care] generation. We embrace our illiteracy." The part in brackets is one I can't remember verbatim. Some of The Longest Journey outtakes are priceless, especially the one where Abnaxus' voice actor says "...and our three female children, Abratha, Ablexe, and oh you've got to be kidding."
But my favorite quote has to be from Grim Fandango when Glottis gets some sweet hydraulics for the car and says, "Manny until now we scraped along the ground like rats. But from now on, we soar... like eagles. Yeah, like eagles... on POGO STICKS!!!!!"
And another Glottis quote I use when interacting with my friends' cats, especially when they meow to me, is "is that you kitty? Don't talk kittty. Juuuuuuuust ruuuuuuuuuuun." It's not a clever, deep, or profound quote by any stretch, but I like it because it's one I actually use and people think its funny when I say that to their cats in the Glottis voice. No, they don't know the video game or anything, but it's too silly for them not to laugh.
EDIT: An RPG quote that I thought was awesome but never even made it into the game (though it was featured prominently in the promo soundtrack CD) was when Kyleen from Thousand Arms says, "Are we going to do anything fun, or are you just going to stand there with your thumb up your butt?"