FFX is a good excuse for buying a PS2. I just swapped my Xbox with a friend for a while so I could play it since little else on the PS2 interests me.
FFX is one of my favourite FFs, probably a bit below FFVII. It has great graphics, a great storyline, and the leveling up system's pretty good (although still slow). In my opinion anyway, many people think the opposite. The soundtrack's pretty good too, better than 8 and 9's IMO.
Our views probably differ greatly though, since I don't really like the retro FFs. FFX is very un-retro, what with the addition of speech, it being in full 3D, etc.
I suggest you try the game before splashing out on a PS2 for it, or maybe you could do what I did and borrow one for a while.