First of all, the story of how Lucifer was cast down from heaven is completely being misinterpreted here. God had created the heavens, the earth, and all life, including the angels and us (meaning humans). One of the things He commanded was all to worship his greatness, and his generosity in granting life to us. Lucifer, however, wanted that same recognition--in essence, he wanted to be as great as God. God perceived this, and cast him down to Hell. Hell, at that point, was not a place of torture as you can possibly understand it. Hell was torture for Lucifer, however, because he was alone and eternally separate from God, his creator. So God, in another benevolent move, gave Lucifer the earth to rule over, hoping that he might see God's greatness in the intricate designs of life and the biological processes as he tended to the earth. The exact opposite thing happened, however--the first thing Satan did was tempt Eve (in serpent form) in an effort to have revenge on God for humiliating him. And, alas, it worked. Satan had his revenge, for the moment, because humans were doomed to imperfection, and thus must be separate from God for eternity. Another motive for Satan to tempt Eve was so he would not be alone in his life--"misery loves company" as the saying goes.
Second of all, most of you have speculated that Satan would much rather "recruit for his cause", i.e., to overthrow God, etc., etc. This is absolutely correct, and it is outlined in detail throughout the Bible, specifically in Revelations. What you're missing, though, is the fact that Satan rules his domain by fear: "...there will be much weeping, darkness, and gnashing of teeth, screaming, and no soul to see, no sight for any eyes except the great chasm, across which you will see Abraham's bosom and what you may have had, had you only believed in Me." Hell as described in popular culture (a place of burning red flames and a dude with a pitchfork running it) is not correct. People who end up in hell are, according to the Bible, being coaxed by fear and a complete disconnection from God into hating Him, hating everything, even Satan. They try to kill themselves (the ultimate form of cowardice), but it can't be done--they must suffer their choices in life in the afterlife.
Finally, how it all ends--the battle in the valley of Armageddon. It's been prophesied that Satan will be defeated for good in the valley, as well as his legions (demons and those who died not believing in Christ). Satan knows this, and knows it well. He knows he'll get his ass handed to him on that day. The worst part of it all, though, is the fact that the sick bastard wants to take as many of us down with him as possible. He knows that every person who dies a non-believer is a blow to God. It's been written that Christ will lead the army of Heaven into the battle, and, before the battle begins, He will weep--but as He slays the non-believers, the demons, every single one of them, He will be ruthless, and His eyes will be like a white flame. When it's all over, everybody on Satan's side will be thrown into the lake of fire for eternal burning, with skin that burns deeply and then grows anew--but the flames will be black, and those within it will be blind to all. "Hell" as you know it is simply a holding cell--the real prison is the lake of fire.
Alright. Before the Christian bashing begins, let me just say that all I'm doing is trying to give an intellectual insight on a subject I know a thing or two about. And, you should all know for your own reference, being a Christian doesn't mean you have to be a "good person". No works you do on earth permits you entrance into heaven--the only ticket in is believing in Christ's sacrifice and accepting Him as your savior. Basically, swallow your pride, because pride's the same thing that got Satan in that hellhole (no pun intended) in the first place.
Also, some have said that God would encourage being "open-minded"--and He does. But on the premise that He gave you that mind in the first place, and the ability to think.
Thank you for your time.