Well, I've played the Magic: The Gathering(tm) trading card game for almost a year now, although I've since stopped as school, and a lack of interest among my friends made playing more difficult. Also, it is a very expensive game to keep up with.
Anyway, here is a brief, if somewhat long analysis of the basic game. (Yes it gets far more complex than this . . .)
As far as I can tell, it is essentially a card-based strategy game that uses resources - cards, mana, life etc. to defeat the opposing player.
To win the game, you must defeat all opponents. To do this, you normally either reduce their life points to 0 (players start with 20 life), or force your opponent to have to draw a card and not be able to (called "decking"). Current rules require decks to contain a minimum of 60 cards. Some cards let you win by other ways, often weird and non-violent. (The white card Test of Endurance causes you to win if you have 50 or more life.)
The during a regular game the table is divided into the library, where most of your deck starts shuffled, the playing field where spells are played, and the discard pile, or graveyard, where used spells and destroyed cards go.
When a game starts, players shuffle their decks, and on the first turn draw 7 cards. These cards go into your Hand, from where they can be played.
Mana is essentially the main expending resource, like gold or money, or food . . . usually you get it by tapping land cards sideways and so adding an amount of mana equal to the amount the land card produces, usually one.
Cards other than lands have casting costs of a certain amount of mana. You pay the cost to play the card. Mana can be one of the five colours, or colourless. Coloured mana can be used to pay the cost of colourless. You can only play up to one land per turn.
At the beginning of each player's turn that player draws one card.
Cards are divided into several types.
Lands have already been explained.
Creatures are essentially any sort of soldier, animal, monster, or thing that can attack and block attackers.
Sorceries and Instants both are usually one time effects, like deal 2 damage to target creature etc.
Enchantments and Artifacts have effects on other cards and game rules.
Lands, creatures, enchantments, and artifacts are called permanents
because the stay in play after being paid for.
Sorceries and instants go straight into the graveyard after use.
The game is divided into five colours.
White is obviously the most similar to Christianity in principle. It is the colour of order, honour, justice, righteousness, equality. Usually a very defensive colour, has lots of damage prevention, life gain, and protection type spells. Common creature types are soldiers, clerics, Angels, knights etc. Interestingly, this is also the colour with some of the most powerful "equal" effect spells, like Wrath of God, which destroys all creatures in play. White is Blue and Green's allied colour, and Red and Black's enemy colour.
In depth on White:
http://www.wizards.com/default.asp?x=mtgcom/daily/mr57
Blue is the colour of knowledge, trickery, and planning. Blue uses deceit and superior tactics to defeat an enemy. Blue's most famous card is the Counterspell, which is used right when an opponent plays a card to counter it and send it directly to the opponents graveyard. Blue is also good at doing various tricks such as flying evasion etc. Blue's creatures include wizards, birds, and sea creatures. Blue is White and Black's allied colour, and Red and Green's enemy colour.
In depth on Blue:
http://www.wizards.com/default.asp?x=mtgcom/daily/mr84
Green is the colour of nature, life, and peace, and so has lots of big powerful creatures, but is weak at targeted removal of enemy creatures. It also can accelerate mana better. Green's creatures include elves, beasts, elephants, etc. Green is allied to White and Red, while the enemy of blue and black.
In depth on Green:
http://www.wizards.com/default.asp?x=mtgcom/daily/mr43
Red is the colour of chaos, anarchy, violence and freedom. Red has good direct damage cards, but doesn't have much staying power. It deals damage fast but then loses if waiting too long. Red has creatures like Goblins, Dragons, and Beasts. Allied to green and black, enemy of white and blue.
Black is of course, the colour of greed, hatred, and malevalence. This colour tends to get the most controversy from Church groups and such. Black has sacrificial cards (ie. lose 5 life when you play this creature), creature removal (destroy target creature) and card discard. Black creatures include zombies, vampires, horrors, and even sometimes Demons.
Side note: Due to the Church groups very much protesting and threatening Wizards of the Coast because of the Demon cards, for a long time, Demons were taken out of the card sets. Very recently, a very few have been added in again, but they are no longer as powerful, and no longer have wings. They are usually depicted either chained, or somehow disabled, according to policy.
Black is allied with red and blue, and enemies with white and green.
As far as power is concerned, the colours are very well balanced, so none are too powerful. Making a good deck is difficult and requires practice, and understanding of game mechanics. Making a tournament worthy deck requires insane play testing, taking advantage of brokenly overpowered cards (there are very few of these) or combos, and thorough strategic understanding.
Reasons the colours are so aligned:
http://www.wizards.com/default.asp?x=mtgcom/feature/14
The game involves a lot of issues to do with efficiency and card-advantage (ie, more cards than opponent through extra card drawing).
The matter as to whether or not it is bad depends mostly on how seriously one takes the game, and whether you can understand the flavour part is all fantasy.
I personally enjoy the incredibly complex strategic management in the game. Of course, I understand that the game is only for fun, and only fantasy. I play mostly for the sake of playing with friends. Also, to further my identity as a Christian, I usually play all-white, or mostly white decks.
I haven't even gotten into the beginnings of the strategic parts of the game, such as combat, the stack, mana efficiency, card-advantage, control vs aggressive styles, turn pacing, special mechanics etc.
Right now my best deck is White Weenie, which just plays lots of cheap soldiers, birds, and knights to overwhelm my opponent.
Big spells actually aren't that great if you don't have the mana to pay for them . . .
To sum things up, the function of Magic is an excellent strategy game, the flavour however, is that of magic and sorcery in a fantasy setting, basically involving two or more mages dueling to defeat eachother.
Anyway I hope this helped a little (sorry if it's really confusing though).
Here's what another forum had to say:
http://www.christianforums.com/t49896
And some Christian articles:
http://www.answers.org/Issues/Magic_game.html
http://cana.userworld.com/cana_magic.html
http://www.pojo.com/magic/StrategyGuide/Jan2003/Jan%2017-2003/Is%20Magic%20Really%20Evil%20-%20Robert%20Overton.htm
http://www.christiangaming.com/CGForum/topic.asp?TOPIC_ID=128&whichpage=2
http://www.probe.org/docs/e-mtg.html
http://logosresourcepages.org/magic-g.html
http://www.londonbiblecollege.ac.uk/features/games/DangerousGames/dangerous.html
http://wastedomain.net/rants/beware.shtml