If you go to your game Q, there is a link that says report a shipping problem. From there you can select the lost or missing sleeve option and gamefly will send you a new envelope and sleeve at no extra charge.
I doubt they would ban used games, they might move to the system that some developers, like EA, have moved too which is an online pass system. The system that locks out content like multiplayer or in Arkham City's case a whole section of single player play, until you enter the code that shipped with the title. If you are playing a used title you cannot play multiplayer or access this content without buying an "online pass" for 9.99+. This might bolster sales of new titles like the game developers hope, or it could cause gamers to avoid those products. This is only my opinion, I hope this doesn't happen as I tend to rent or borrow games before I buy.
If you are going to play it, you should check out off the record, it is basically DR2 with the main character from dead rising instead of chuck greene. It has additional areas and a free play mode that more than makes up for the lack of the main character from Dead Rising 2
This happens to me all the time. I have several available titles in my top ten and end up getting something thats at the bottom of my list, or in one special case I received a game I didn't even have on my Q. When I've filed a complaint to gamefly they give me the generic answer that you're top games will not always be available and thats why you should have a full Q. I replied with how my top 5 were available now, from when they received one of my games to a day later when they shipped out the 30th game on my list. I sent them a screen shot of my Q that showed that the games were available and they still gave me the spiel about only putting games in your Q that you want and making sure you have a full Q for when your top games are not available. In my opinion, since Gamefly took off and gained more subscribers, they hired more people on( Probably migrant workers) who just stuff the envelopes with whatever game that can find off your whole Q and dont pay attention to the order.
In all my years of gaming, no game has disturbed me more than Dead Space 2. I had the hardest time playing it, it seriously freaked me out. Another creepy game thats a little older would be shadow man. That game has some seriously messed up areas, there are times where there are demonic whispers,children laughing and talking about killing people its messed up.
I would jump on the bandwagon and say a COD title, but the problem is that the multiplayer is the best part and sooner or later (mostly when the newest installment comes out) the systems falls to hackers and the MP is almost unplayable. Its really sad, because my favorite MP experience in the past 5 years came from MW2 and thats like a wasteland at this point. If it had to be a current gen title I would go with Fallout 3, or maybe Fable, as there is a ton of stuff to do and multiple ways you can play ( evil or good). If it could be any title I might go back to the snes and pick maybe earthbound or Final Fantasy 6, can't go wrong with a good classic RPG. A good fighter would be Marvel vs capcom that still blows away most newer titles. ( tekken, soul calibur, etc.)
I'm pretty sure that whoever is working that day just picks the easiest games on your list if the pick anything for you at all. I've gone for a couple of days where I had two games that they should send, but they don't send me anything. Sometimes they send games at the bottom of your Q when games at the top are available now. I don't really think the workers follow the system I think some might, but the most part is that they have a bunch of douchebags working there who grab the first game they can find off your list and send it.