.dat (presumably being short for data) is probably the second most common "I just need an extension for this file as the operating system/compiler/whatever demands it", with .bin being the first (.pck/pak/variations on the theme of pack being third). To that end there are probably a thousand file formats, radically different, with .dat as an extension among PS2 games and you could probably find, and in any given game I would not be surprised at all to find multiple .dat files with radically different contents/formats/uses.
The PS2 SDK did not seem to provide a common text handling format that all the devs hurried to use (compared to say the DS where there is one that many did use, and if we are talking about audio formats then those can be quite common between games on a system as rolling your own audio format is a nightmare).
That said I would look at such files as a matter of course, especially if directory names or file names would indicate it (or eliminate other things).
Topic: Does the .dat file in ps2 games store the text? (Read 537 times)