Hal's origin: "I shall give the ring to the strongest, bravest human being on the planet with the whitest teeth and perfect physique and skill to match." How is this in anyway remotely interesting? It's like if Superman got the ring, a rocket ship, and Spider-Man's girlfriend, plus a lifetime supply of Baby Ruths. His descent into evil was the best thing to ever happen to him, like in the classical tragedies where the hero is a King (that is, the perfect specimen of man) with one character flaw that brings about his downfall.
He was pretty compelling in the "New Frontier" comic, though. Because it wasn't a classical interpretation of the character.
Kyle: Average Joe gets the ring in the middle of a huge crisis amongst the Green Lanterns. Has no idea what to do as he's tossed into something he didn't ask for. Supervillains left and right are suddenly clamoring to kill his girlfriend and stuff her in his fridge. Now that's fucking interesting. Plus, he's an artist, which makes for great use of his ring visually (which was very well put to use in JLA), which is why John Stewart can't do anything but create green bubbles in the Justice League cartoon, due to his utter lack of creativity. Very utilitarian and such.