Someone here aside from me has read
Yahtzee?
Uh yeah! Don't be so pants-on-head....
Regarding the topic, I tend towards good characters, but I think being evil allows you to explore just how much freedom there is in the game. With being good, there's not usually so much choice between being nice, and then being even nicer, which usually just gets you more quest rewards.
With being evil however, there's being evil while staying in the quests, the given evil option. A good RPG however, will allow you to go apeing bonkers bananas psycho, usually in fairly inventive ways. I remember being quite impressed delving into proper RPGs like Fallout (the original one) after years spent playing games like Deus Ex, which, while good, made certain key characters invulnerable at various points to avoid the storyline getting too mucked up.
While one can be a jerk within the framework of the quests, Fallout is one of the few games I've played that allows you to opt to massacre any and every living thing in the game, eschewing quests for pure evil powerlevelling, which I found rather impressive.
The only other game I've liked being evil on is KOTOR, because you're just so overdramatically evil every time I make an evil choice I start giggling, and also you're wielding two red lightsabers and can fill an entire room with lightning.