I stiil find it hard to believe that Sony engineered such a crappy DVD-ROM drive for the PS2.
I remember reading, although I've never been able to find it since, a press release from around 1999 talking about how Sony had engineered a way to make optical drives for their at the time up and coming console with something like 30% fewer parts.
IMO most of the problems come from two distinct points:
A) The drive assembly is open to air, as is the laser. Check out pics of disassembeled units on the web. Compare with a PC DVD-ROM drive, where the unit itself is sealed, and the laser eye is sealed so that only the top lens is accessible. Not so on the PS2.
B) PC DVD-ROM drives auto-adjust their read voltage and wavelength to suit the disc inserted. This has been true since so-called 'multi-read' CD-ROMs capable of reading CD-RWs came onto the scene. The PS2s drive does not auto-adjust at all; it has two pots on a control board, one to control CD read voltage and one to control DVD read voltage.
What really fascinates me (I work at EB) is how these Sony sack-riders will bring us their broken PS2s and get a new one, without any sort of resentment at Sony. My, how the sheep have been trained.