The PS3 is a gaming console that happens to play BDs. I never considered the PS2 a DVD player. I know it could play DVDs but I never thought of it as one. Just as I never hear anyone talking about the 360 being a DVD player...
Probably because the PS2 offered a mediocre-quality DVD player, with the inconvenience of a gaming machine, for a higher price than comparable stand-alone DVD units. In other words, there was no compelling reason to buy one for DVD playback.
The PS3, by contrast, offers one of the best-performing BD playback among all options, provides wireless connectivity for firmware updates and eventual upgrade to profile 2.0, will be upgradable to profile 1.1 and DTS-HD MA decoding (offering the fullest featureset of almost any player available), and costs the same or less than comparable stand-alone BD players.
The differences are obvious and familiar to most everyone with even a modest knowledge of the PS3 and HD media.