Xbox is not live (online) out of the box. you still have to pay a 40 quid subscription in the end.
for the casual gamer, or the beginner... I wouldnt hesitate to say the PS2. XB is good, one look at halo will confirm this, but at the end of the day its just one game (well until the second one comes along
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the XB is really just geared around live play. so if you aren't going live then you will soon get bored with the lack lustre release list. if you are going online then its well worth a look at.
the PS2 basically just has more. its a great primary system. the Xbox and GameCube are great secondary systems. I could never live with just the XB or just the cube.... I would end up trying to scalp my self with a rusty spoon or something.
if you like football, the PS2 has the best choice. if you like racing, it has the best choice. if you like other sport games, it has the best choice. if you like action adventure, it has the best choice. if you like arcade games, it has the best choice... you see where im going with this...
there are true classics in the back catalogue too.
graphically the XB is the most powerful. but as yet no game has shown the true potential of the system. my view is that the GC has produced the best looking games so far. and although old, the PS2 is no slouch in the graphics department either. look at the more experienced developers games to justify this.
the XB outputs DD 5.1 through a separately acquired cable. all games support this. its a MS requirement.
the PS2 can out put a variety of sound. most common is pro logic II. less common is 5.1 as this uses processing power of the machine. and then there is the DTS support. games such as SSX3 and GTAVC use this feature. but overall the XB is the sound mans choice, especially when you can create custom soundtracks.
personally, I would rate them in this order:
PS2. Basically it has the most games that I prefer to play on it.
XB. massive potential. online leader. iffy one player though.
GC. slow and steady. when the good games come they dont disappoint.
so to answer your question.... buy all three. problem solved