Grab this gem that easily trumps Mass Effect and KOTOR.
Reason the First: the maps. KOTOR's maps... complete **** In Mass Effect, the perimieter of the map was defined with walls or mountains. In Jade Empire, paths carved through the natural terrain, so that the perimeters were definsed by believable rock formations, impassable terrain (that actually varied), gates, rivers, etc. In KOTOR, EVERY DAMN MAP took place in a recessed valley, around which a seemingly unclimbable mesa (seven feet in height) enclosed your adventures. LAME.
Mass Effect's maps made me feel like I was an ant trapped in the grand canyon; ****loads of open space, VERY little to do in there. And are you telling me that EVERY inhabitable planet has only one or two plains on which to build a settlement/lab/etc.? Didn't the environmental artists realize that you could define the perimeter of a map in ways OTHER than using impassable mountains? Furthermore, the planets used on all of the side-quests looked like the artists made a color-swap. "...erase color = red... add new color = green... Ok, THAT planet's done."
Reason the Second: combat.
In KOTOR, you clicked on the ugly red ovals that appeared above your character's head. A box with a diagonal line apparantly meant you would use one force power (that in the movie would create a severed-head, but in this game only a scratch), while a circle meant you would throw a grenade. Of course, these ovals would dance around as your enemies moved about the battlefield. Click enough unintuitive shapes, and you could win the battle.
In Mass Effect, the combat could have easily used an additional round of polish. Most battles went something like this: one enemy rushes me, strafes behind me in a speed that I can't match, and shoots at me from behind; which the other enemies fired from the distance. Not only could my character not turn on-the-spot fast enough to pursue his quarry as the enemy ran around him, but he also would get stuck against any wall or box due to the brilliant cover-system that does not utilize a button to enter or leave said cover. Brilliant.
Jade Empire used four buttons: attack, block, power-attack, and slow-motion. Keep it simple, stupid.
Reason the Third: setting. While each game's story was barely good enough to get my interests, the settings showed me one thing: Bioware can't do space well (yet). KOTOR felt generic mostly due to its poor maps. Mass Effect felt more original, but again fell flat due to its poor side-quest maps. Grounded enough in the familiar but altered enough to be intriging, Jade Empire was set in a fictional land in East Asia (based on China, I presume), which helped sustain my all-important suspension of disbelief.
I summarize each game as follows: KOTOR was an ok game with a decent story (but great plot-twist) and ****ty maps everywhere. Jade Empire was a fun game with a decent story and good maps. Mass Effect was a (mostly) extremely polished fun game with an ok story, and mostly ****ty maps.
Jade Empire > Mass Effect > KOTOR