Death Note and Fun

Right? Light should have become God, not lost to some discount L.

Meh, I disliked the ending as well, but I think Light was too far gone to keep any of this up for much longer. Besides, if the stress and psychosis didn't drive him to suicide early on, eventually he would die. Despite what he thought of himself, he's still only human - sooner or later, something will kill him, even just old age. And then, even if he HAD managed to purify the world by killing off all the criminals, the world would just revert back to its previous crime-infested state. The whole concept of the show, at least how I saw it, is to emphasize how small we humans are in the grand scheme of things, illustrated by Ryuk's presence throughout the show and his final "it's been interesting," or whatever he says. If Light won, that aspect of the plot is lost.