What made you think it was a PC in a box? The CPU was an SH4 not x86, it had it's own bus (not PCI) and the graphics chip, CLX2, had numerous features that were certainly not part of, say, DX or OpenGL.
You mean what made you think. Back then I thought it was what the Xbox 1 would later become, but with a GeForce2 at its heart, and polygon specs that I felt would soon be very outdated.
As I said, today I would have a more nuanced view.
PS2 had some fast FP hardware plus loads of fill-rate but only with very simple blend modes, which it achieved by using a 'hectare of silicon'. If you do some searching, you can probably find the B3D post I made many years ago which listed most of the leading-edge features of DC's graphics.
It is people like you yourself who have helped me understand the differences better. Nevertheless, at the time the Playstation games impressed me a whole lot more, and I was a firm believer in the value of integrated DVD. I don't think I was all wrong at the time in preferring the PS2 hardware, but like I said, today I have a much more nuanced view, due to just knowing a heck more about hardware and programming then I did back then (although I wasn't completely clueless, having at least attempted to program the DSP on the Atari Falcon).