I ran into Minecraft about three years ago, and have honestly not been interested in playing another video game since.
I play multi-player on a PC and my personal goal set is exploration, contraption engineering, and making giant structures/playsets/puzzles for my son, and our friends to play in.
I think that what makes the game so spectacular is the fact that it almost perfectly encapsulates, or at least offers the building blocks you need for almost every play style, and makes it so that you can pick and choose exactly what game it is that you want to play. It can be an exploration game, or a fighting game, it can be competitive, it's a collection game, it's a creative building game where you show off your collection and achievements by creating things that people can wander in and around. There's resource management, it has aspects of being a first person shooter, there's hack and slash. It can be a platformer, or a maze game. It can be a survival game, or PvP, or a sim...
To answer a couple of Janx's questions:
I'm assuming that you're playing the X-box version. I'm guessing that it will eventually give you the ability to download other people's maps, like you can on the PC version. A lot of those maps are "adventure" maps, basically self contained RPGs built using Minecraft as the framework. You can occasionally find multiplayer servers that will run those downloadable maps as one shot games.
How to capture AND contain animals so they don't spawn out?
Eventually, your version will let you use things like wheat and seeds to get different animals to follow you. In addition they'll eventually catch up to the PC version and stop animals from accidentally spawning through walls and fences.
How to stop monsters from spawning inside my lighted house with multiple closed doors despite being lit every 12 blocks?
That just means that there's some corner or hallway that's too dark.
How to dispose of a creeper that is trapped on the top floor of my fort without blowing him up? There's a sanded off stairwell above and below him so he can't escape, but it makes getting to him more complicated.
I would assume that the X-box version mobs work basically the same way as they did in the same build of the PC version. You should be able to just walk a good bit away from the tower and come back and have him be gone. Does anyone know if they're persistent on the X-box?
What is Normal or Hard difficulty like (We're playing on Easy because that's what the tutorial started at). Our method of building keeps us indoors at night, so we seldom deal with monsters.
At least in the PC version, the difficulties change monster damage, hit points, and behavior, and affect player hunger and starvation.
Besides the terrors of the NetherWorld (never been), do the dangers in the OverWorld ever increase? Creepers are currently the most dangerous enemy. They are out 24/7 and the explode, destroying structures and thus letting in more enemies.
Eventually you guys will have Endermen, Spiderjockeys, Withers, and whatever other future monsters are in the pipeline.
It would be interesting if things escalated, to further justify all the fortifications we built. Otherwise, it's all rather siller over-engineering.
This is why some people prefer PvP.