If you look at it, Lucifer was only exiled from Heaven because of his refusal to bow down and serve humanity, whom he considered an inferior race. Considering he was one of the first two sons of God, in the form of Samael, and was nearly the embodiment of Free Will itself, what he says when challenging the heavenly host does make sense, “If all God wanted from me was obeisance, he wouldn’t have made me capable of thinking for myself.”
Further, though there is a lack of consensus as to his motivations [He wanted to rule mankind, he wanted to take over heaven, he wanted to overthrow God as the supreme being], his intentions are believed to have been one, and not that ignoble, namely: To escape out of God’s plan. In other words, all Lucifer wanted was to not be a pawn or a puppet.
Lets take a look at the “facts”:
God’s first two creations/sons were Samael (Lucifer) and Michael, and he used Lucifer to bring Stars and galaxies and Suns into existence, while he used Michael to bring “Life” into these Worlds, thus completing them. It’s after this that he created the Heavenly Host, which is the rest of the archangels, as well as the regular angels. Michael and Lucifer were always closer to each other than to the others, because Lucifer accepted that Michael was the “elder” (eldest) brother, and listened to *no one* else.
God himself loved Lucifer most, even more than he did Michael, because Lucifer was sharp and keen and never missed a thing, and God considered him his most perfect creation, especially in the way he searched the Universe for new and fascinating things, bringing them into existence by observation (which was originally the point of angels, before humanity was created).
About this time, because Lucifer was so awesome at stuff, and because Michael was not half as ambitious, God determined that Lucifer should watch over Earth, and Lucifer was absolutely fascinated with all life, and this period includes the dinosaurs, the first mammals, etc.
However, once Mankind was created, Lucifer was constantly in conflict with God, as well as the other angels, because God asked all of the angels to serve mankind, and Lucifer was convinced of their imperfection, which he held in contempt. He saw humans as treacherous, murderous beings, and refused to venerate them as God wanted. These arguments he kept having convinced quite a few angels (namely 1/3rd of the Heavenly host), but the majority of Heaven saw his words as ungrateful, and saw him as someone trying to take over the Throne of God.
Around this time, God suddenly cuts. And, the burden of ruling/governing heaven falls on the archangels. Michael sits himself in the tower of God, all depressed for having been deserted by God, but still governs it in terms of making decisions, and watching over everything. Lucifer first goes to Michael, and tells him that he doesn’t trust humans, and that he believes them to be even more vile than the beasts over which he has watched for millions of years. Though Michael loves Lucifer greatly, he sees Lucifer’s words as dangerous, and quite a few angels had already filled his tired mind with poison regarding Lucifer and his intentions. Harsh words are exchanged between the two. And, Lucifer basically tells him, “Bro, you may be the older brother, and our father may be God, but no one is the Boss of me.”
After a while, the arguments turn into full out rebellion. Though, the clever way the holy book never tells us what exactly started the war leads me to believe that Lucifer did not start the War, per se. Anyhow, once it did start, it was madness and chaos, and, of course, no one is as bad ass as Lucifer, so he started kicking everyone’s ass. I know Gabriel played a large role in what happened next. Because, he was the only other angel that both Michael and Lucifer equally loved and trusted. Anyhow, I think he runs to Michael, and tells him that Lucifer was going to get himself into trouble, and that he (Michael) had to stop him. Michael relents, and shows up with his sword, and Lucifer taunts him for being nothing more than a puppet of God, and Michael finally loses his temper, and they start fighting like crazy, and Lucifer takes on the form of a dragon [coz I think he really liked the dinosaurs :\] and they’re all going at it like a bunch of quarrelsome little boys. And God comes back, and he’s like, “What the..?”
And, Lucifer says “Humans suck, God! And I don’t wanna serve them! And, I’m your son, not your slave! You gave me the power of free will, but everything any of us do, it’s all supposed to be within your ‘plan’. Well, I can’t take it! If that’s all I am to you, I’d rather be nothing to you at all! I want out!”
And, God said, “You want your own realm? You wanna be free of ‘My Plan’? You want to truly exercise your free will? And, prove just how despicable human beings are? Well, I have just the place for you!”
And, Wham! Lightning strike to Hell. The first son, exiled. Made an example of. But also freed without God having to change the rules for everyone. Also, he got someone to look after Hell. If the most flawed and disturbing humans could see this perfect being amongst them, maybe God thought it would be an even better prison. And, which other child of God was capable enough of dealing with the worst of humanity? Why expose his angels, who were supposed, and required, to believe in the goodness of man, to the kind of filth mankind is actually capable of? And, after all, mankind was a kinda experiment… If Lucifer was right.. well, God knows that he (Lucifer) can handle them all.
[Okay, this last part is all just me trying to make sense of God’s decision. Because, he really loved Lucifer. And, how can you be so unfairly cruel to something, or someone, you claim to love?]